Thank you Dave.
If you can give a specific example of a transformer or choke that maintained its part number although the specs had changed, I'd like to study the issues.
-al hart, w8vr
OK, look at the UTC S-35 chokes. In the 1949 catalog they were listed as 20hy, but by 1955 they were 8hy.
The Stancor C-1415 were 6hy @ 7500V in 1948 but were 8hy @ 5000v in 1939.
I also have a Thordarson power transformer (I forget the number) that is listed at two different output voltages depending on which year's catalog you look in.
I have Merit A-3110 modulation transformer that has different impedance ratios listed in the 1951 catalog than the ratios listed on the label on my transformer. I also have a Merit filament transformer that has different voltage specs from one catalog to another.