Ernst Deffner's PANcordion and Titano deals with Estey for the supply of OEM (Original Design Manufacturer) rebadged amplifiers was large enough that Estey made circuit and design changes that were unique to these amps (probably at the request of Deffner to better integrate with some of the accordions those companies were selling).
The Titano 383 is a good example of that special agreement. Notices the special DIN-4 connector and threaded coax above that.
I believe these were similar to the 280B, and was produced as one of the early Estey Titano's in 1961. Later, reverb was added to the Titanos as Estey adapted it to the 400 series amps.
If anyone more information or a schematic for the 383, let me know.
This Titano is forsale at jayrosen.com Photographed by Sibila Savage Photography.