[Arran]

Arran, Let's see if I have this straight. There are only two chassis codes for the 38-116XX --121 and 125. You are not saying there must be a 122, 123 and 124. Only that the 121 was first production and if there were a 122 there would also have to be a 123 and 124 since the 125 exists. Correct? The second chassis could be any number? Why 125 and not 122?

Anyone else get brain cramps? Luckily baseball, even MN Twins, eases them.

What I am saying is that if they produced a chassis as a code 121, then the next in line would have to be a code 122, if there is a code 125 then there has to be a code 122, 123, and 124 version as well. What I was trying to say is that the code numbers represent different production designs not production runs, Philco would often alternate between different production code designs during a production run depending on what parts they had on hand, and that doesn't include running changes to improve things. So if they had the tubes on hand for a code 121 they would build 121s, if not they might build a code 122 or 123 etc. depending on what parts they had on hand. If there were only two production versions they would use a code 121 and then a code 122, as far as I know they would not skip numbers and build a 121 and then code the second version as a 125 with no intention of building the other versions. You can't use Nostalgia Air as a complete reference to this, the schematics that they have listed are whatever someone decided to post, you would need the complete service data from the factory. Getting back to the 46-1201 for example, there were eight code numbers from 121 through 128, however Nostalgia Air only has one or two diagrams but the others definitely exist in the Philco Factory data sheets. If you are used to Zeniths this will drive you nuts but it was Philco's way.
Regards
Arran