Supro amp serial number dating
Transformers and Speakers were ordered in smaller quantities, and pots in very large quantities.
Number Date 2000 - 3000's 1949 or 1950 4000 - 5000's 1951 5000 - 6000's 1952 6000 - 8000's 1953 9000 - 12000's 1954 12000 - 16000's 1955 17000 - 21000's 1956 22000 - 26000's 1957 27000 - 30000's 1958 30000 - 34000's 1959 34000 - 39000's 1960 39000 - 45000's 1961 46000 - 52000's 1962 53000 - 63000's 1963 63000 - 84000's 1964 New Serial Number Scheme 1965 to 1972 The first 2 digits show Month (Jan = 1 and Dec = 12).Although the envelope was classically glass, power tubes often use ceramic and metal.The electrodes are attached to leads which pass through the envelope via an air tight seal.Also, the badge plates were different on the very early Customs, eventually they were produced with the large "M" (below right).It is possible that the first models had yet a different plate than the style of the early M7 plate below. are unknowns but it might have been due to re-order supplier issues for the standard emblems during the bankruptcy of 1964-1965.On most tubes, the leads are designed to plug into a tube socket for easy replacement.
The simplest vacuum tubes resemble incandescent light bulbs in that they have a filament sealed in a glass envelope which has been evacuated of all air.
Estey simply had a large bin of pots that lasted them a year.
Serial numbers show approximate date of manufacture.
This page contains details about the 1963-1966 Magnatone Custom Series amps.
For an overview, see Magnatone Custom Series, or for a history of the Magnatone amps from 1947-1977, see The history of the Magnatone brand.
These electrons will be drawn to a metal "plate" inside the envelope if the plate (also called the anode) is positively charged relative to the filament (or cathode).