In 1955, Magna President Art Duhammel hired Paul Bigsby to design some electric Spanish style guitars to be sold along side the steel guitars and amplifiers in the Magnatone catalog. Bigsby and Duhammel already had a working relationship with some the Magnatone steel guitar design and consulting work, so collaboration for the new MARK series guitars was natural progression.
Electric Spanish guitars were still somewhat of a new invention by 1955. Leo Fender's first electric guitar had hit the market in 1950, and Les Paul's Gibson offering had followed in 1952. Duhammel had the right guy with Bigsby, too. Bigsby was as much of a pioneer as Leo or Les with his one-off guitars built for guys like Merle Travis and Grady Martin.
Designing the guitars was one thing, and production of them was another. Bigsby had no interest in monitoring the production of these guitars, and furthermore, by all accounts, it seems that by 1957 or so, he was completely burnt-out on building or designing electric guitars for anyone. After designing these guitars for Magna, he shifted his focus to his own company's production of the Bigsby Vibrato Arm, which was sold as a boxed unit, for individuals or manufacturers to install on their guitars. The Vibrato was a simple assembly that was made of cast and stamped steel parts, and was easily assembled. There was no finicky wood to expand, absorb moisture, and crack.
As for the Magnatone electric Spanish guitars, by all accounts, Bigsby only designed the guitars. All production details were left up to Magna. There were two guitars designed and sold between 1955 and 1957.
The first guitar was the Mark III and the Mark III Deluxe, and the second guitar, which appeared in Magnatone catalogs about 1957, was the Mark IV and Mark V. Not many of either of these guitars were built, and both were offered concurrently in the 1957 catalog, with production lasting into mid to late 1957.
Also it should be noted that the only Magnatone guitar that Magnatone credited to Paul Bigsby in their catalogs was the Mark-V. The catalog's Mark III guitar description does not mention Bigsby. The Mark III and the Mark V appeared in the same 1957 catalog. Also, the build and finish differences between the Mark III and the Mark V are significantly different. Although the Mark_III guitar were known to be produced at the Inglewood factory, it is possible that the Bigsby Mark V was produced elsewhere.
The first production guitar was the Mark III followed by the Mark III Deluxe. These early Magnatone guitars were sold at much lower price than the Fenders and Gibsons. A single pickup Esquire listed at $150, and first production Magnatone/Bigsby guitar, the Mark III, listed at $89.50. It was a single pickup, mahogany bodied guitar, with an "M" stamped in the tail piece. A selling point of the Mark III was the Perfecto-Tuned offset bridge with four way adjustable string guides. The neck was built with a U-channel shaped steel re-enforcement (non-adjustable), and covered with a hardwood fretboard.
Although, they were made of mahogany, most if not all of the early Mark III guitars were painted an opaque "Desert Sand" beige finish. The $89.50 list price most-likely mandated the selection of pieces of mahogany that were probably not suited for natural finishes.
The dual pickup Mark III Deluxe model was added at some point, as were a few other opaque finishes (red and black, at least). Another significant aesthetic change was the adoption of a formica pickguard that was full body shaped and extended to the edge of the guitar body.
Magnatone built a Mark III with the name "Lyric". The name was etched on a plastic headstock piece instead of the Mark III moniker, and the body was fitted with the full body shaped pickguard. This was probably a move to cut assembly and finish time.
To further drive down costs, the original thru-body neck design was discontinued in favor of a set-neck arrangement. Wood materials also varied including maple necks and bodies.
The earliest 1955 guitars were neck through designs and had hollow side wing sections. This was changed to a solid body with a set-neck by 1956.
The Mark III and Mark III Deluxe were offered in 1957 catalogs along side the the Mark IV which was introduced in 1957. The III Deluxe was fitted with the chrome control panel and knobs from the IV. On the Mark IV, theis control setup fits and looks nice, and it is a little crowded on the smaller Mark III body.
The second Bigsby designed guitar that made it to Magna production was the Mark IV and V models. These were both really the same guitar except that the Mark V came a Bigsby tail piece, and the Mark IV came with a set tail piece. Materials were Honduran Mahogany and Basswood, and the mahogany neck was a set neck design like the Mark III (as opposed to a bolt-neck design). Initially, both guitars had a german carved top, but at some point, the carved top feature was dropped from the Mark V.
Major endorsements came from Bob Gibbons of the Tennessee Ernie Ford Show and Gene Davis.
Whether these guitars were built at the Magnatone facility in Inglewood, or elsewhere is unclear. The production span of 1956 through 1957 straddled the Magna ownership change of early 1957 when Duhammel and Hellman sold the company to Chilton, Buckles, and Walsh (see history). By this time, Bigsby had moved on to other projects, and the new owners were left to find a new guitar designer.
In 1957, for the Mark IV, a new Alnico 6 pickup was adopted to both steel guitars and the new Mark guitars.
Magna executives next hired Paul Barth to design the next series of Magnatone Spanish style guitars. Barth had just recently parted ways with Electro String, for whom he had worked as a factory manager and designer for many years. In the mid-fifties, Barth designed the Rickenbacker Combo 600 and 800 guitars for Electro String. As iconic as the Ric Combo guitar design has become, it is amazing that Paul Barth's name is not more well known. That design is basis of what became the signature design accents of the Rickenbacker guitar.
The first guitar to come from the Barth/Magna collaboration was the Mark VI bass, for which production began between January and March of 1959. The headstock was symmetrical, with two tuning machines per side. The single pickup pickup used 4 individual pole pieces and Alnico VI bar magnets. Alnico VI is not as common a pickup magnet as "II" and "V", but "VI" was experimented with and used in the fifties and sixties (it is considered to have a darker tone). The neck was maple, with a Brazilian Rosewood fretboard and dot inlays. The body was a solid piece of wood (unlike the other Barth/Magna guitars soon to come).
There were also some single pickup Mark VI six string guitars thought to be produced (if they were produced, they were done so in very limited numbers).
The design for the Mark VI was somewhat unique, although the similarities to the Barth's Rickenbacker guitars can be see in the lower cut-away horn.
Magna initially planned to build the guitars at their Inglewood facility. Unfortunately, Magna production staff had terrible problems building these instruments. Magna put skilled assembly workers on the line, but they didn't hire any real luthiers to supervise. As a result, more guitars ended up in the dumpster than they were able to actually ship. Barth was brought back in to sort out the manufacturing problems, but it was decided that Barth would build guitars for Magna at an off-site facility and provide finished guitars with the "Magnatone" name on the headstock. The guitars that resulted from this change of plans were the Mark VII, VIII, and Mark IX, or, the Artist Series, as Magna would label the line in catalogs.
Rather than build the original designed for Magna Mark VI's, Barth's new agreement with Magna was to simply re-brand an existing line of guitars that he was already producing under his own brand Barth Guitars. Luckily for Magna, these were quite a bit more stylish than the Mark VI. This design, what Magnatone would call the Mark VII, originated several years earlier, maybe in 1956 or 1957 when he left Electro String. Barth had a relationship with Natural Music Guild of Santa Ana, CA, for either the production or the distribution of Barth Guitars at the same time he started providing these guitars to Magna with the Magnatone name. 
The Artist Series, as Magnatone sales literature would call the series, launched sometime later in 1959 and included three initial double-cut-away models: the Mark VII,VIII, and IX. Later, a high end Mark X Deluxe Stereo guitar was also advertised. Unlike the Mark VI, the headstock was non-symmetrical but still used a 3-a-side tuning machine arrangement.
These guitars were
priced in the $140-$200 range with the exception of the
stereo Mark X which was a pricey $350. These list prices
were set for head to head competition with Gibson
All the pickups on these guitars were Barth designs with Alnico #5 magnets. Pickups were mounted to a pressed fiberglass white pickguard that Barth subcontracted manufacturing to a local plastics company. The necks were bolt attached, with a pair of screws on the back side of the guitar, and one under the pickguard behind the neck pickup. Although the body looked to be a solid body design, it actually had hollow sections internally.
The 150 belongs to British rock guitarist and collector, Paul Brett. The photo of the 200 is courtesy of Noah Miller of oldfrets.com
Sometime in 1960, The guitar line was redesigned and the new models were designated the Model 100, Model 150, and Model 200 guitars. In many ways, were continuations of the Mark VII and Mark VIII. Like the earlier series, the 100/150/200 guitars were outsourced to Barth Guitars and manufactured elsewhere in the Los Angeles area. These were included in the 1961 Magnatone catalog and were produced as late as 1962.
All three models carried a rosewood fretboard on a maple neck which was bolted to the body. Like the previous Barth guitars, these had a hollow body construction that the catalog described as "watch case" construction with a top sound board the catalog called a "tone board". For some of these, the top and bottom of the body were glued together, sealing in the pickups and controls. This makes servicing these items impossible without cracking open the "watch case".
Some of these had a natural finish headstock, and some were made with a black headstock and a new "Magnatone" logo was printed in gold letters lengthwise. Barth designed a new tilt neck that let the angle of the fretboard and neck be adjusted with a set-screw accessed from the rear (this idea was carried over to the Starstream guitars).
The Model 100 was a 3/4 scale student guitar. The 150 was a full size guitar with a single pickup, and the Model 200 was the two pickup model. The catalog shows the 100 with screws holding the top board to the body along the perimeter, but other 150's were produced without this convenience.
In fact, regarding all three of these models, it is difficult to say any one aspect was standard for all models produced. There were some that made using some pickup rings and pickups from the older Mark V's, and others used the new style pickups Barth was building at the time. Some had bodies with edge binding while others did not. Some used Beryllium brass bridges, and others used aluminum.
: There are no records of how this actually transpired, I pieced this together from accounts from Lee Burch, an original Magna employee, and various records of surviving Barth and Magna guitars. Likely, the story goes like this: Barth gave Magna a unique Mark VI design, for which Magna was unable to reliably produce. Since Barth was successfully building guitars under his own brand, Barth offered Magna a deal to re-badge his own guitars as Magnatones. Magna agreed to this arrangement, and thus the Mark VII,VIII, and IX were born. A few original Magna-produced Mark VI guitars made it out the door, though very few. The Inglewood production of the sturdier Mark VI bass out numbered Mark VI guitars, but probably not by too much.
: the Les Paul Jr was $130, the Les Paul was $250, and the Les Paul Custom was $375.