Hawaiian guitars were a huge fad in the thirties, especially in southern California. Hawaiian guitar studios were popping up all over the growing Los Angeles metropolitan area. These studios were dedicated to teaching students how to recreate the sounds of the south pacific with guitars and amps (that the studios conveniently sold..), and why not? Students could walk out of their first lessons with a simple melody at their finger tips (try that with the flute or piano!)
The origins of the electric pickup started with the Hawaiian guitar. It was the need to electrify it's sound that spawned the guitar amplifiers of Dickerson (which became Magnatone), Rickenbacker, and early White/Fender amplifiers. Hawaiian guitars were the only stringed instruments sold by Dickerson & Magnatone until 1956 when the first Spanish style guitars were released, and even then, the production numbers of the Hawaiian guitars were much greater than the Spanish guitars. Rock-n-Roll and Leo Fender would soon change the course of electric guitar, "Guitars" would become "acoustic guitars", "electric Spanish guitars" would simply become "Guitars", and with the adoption of the Hawaiian guitar into country western, the "Hawaiian" would become the "steel guitar".
Design advancements of the steel guitars began in the early fifties when professional musicians began to demand multi-neck guitars, and 8 string guitars. Magnatone President Art Duhamell hired consultants, most notably Paul Bigsby, to help improve the guitars. For the most part Magna literature doesn't start crediting Bigsby with the steel guitar designs until after 1957, but he was involved much earlier in the 1950's with all of the steel guitars.
Production of steel guitars is known to have continued until at least 1959. It might have been coincident with the 1959 move to Torrance.
The basic, student model guitar was a single pickup, six string guitar that was manufactured from the the thirties through the Paul Bigsby designed G-70 of 1957-1959. The plastic pearloid finish, AKA mother of toilet seat (MOTS), was used on the student six string steel guitars through 1959. These MOTS guitars were sold with pearloid covered matching amps. Through about 1956, there were several amps in MOTS, but for 1957-1959, the matching amps most likely where the basic AC/DC circuit and the Varsity amps that were single 6V6 SE models.
The MOTS guitars and amps were made in small batches through 1959. The process was difficult to maintain in smaller batches as the fifties wore on. It took a special set of skills to be able to wrap the guitar or amp in this plastic quickly before it hardened. The chemicals used in the process smelled awful, and travelled throughout the plant and for several blocks. When plant workers caught a wiff as they approached Inglewood for their shift, they knew they were in for a few days of that awful stench.
Premium six string lap steels were sold as well, like the "Varsity" of the mid fifties or or the G-65-W6 Troubadour of 1956-1959. The G-65-W6 was a hand-rubbed lacquer finish on solid walnut (The "W" in G-65-W6). An eight-string G-65-W8 was available as well.
Magnatone made double neck eight string guitars from maybe 1952 through 1959. These were call The Lyric. Early models were called the D-8, by 1953, it was the model G-1745, and in later years it was the G-85-DW. These guitars were available with a set of legs at an extra cost.
Three neck and four neck steel guitars were also produced in small numbers. The three neck Maestro was known in later years as the G-95-TW and the four neck model, the G-105-QW, was known as The Quad.
The last of the steel guitars were produced sometime in late 1958, possibly early 1959. By this time, Magna had outgrown their small three building facility in Inglewood. Magna owners moved Magnatone operations to a new 40,000 square foot facility one hour south in Torrance, California. The equipment and tooling for the steel guitars was never reinstalled in Torrance.
My knowledge of steel guitar history is limited. There are steel guitar forums with people much more knowledgeable.
If anyone has additions or corrections to this information, please contact me.