[Arran]

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.

Not necessarily. Philco's 38-116 was produced only in Code 121 and Code 125 flavors. There is no factory data on any other production codes for the 38-116, and as no other codes have been found, we can assume there are only the two production codes for this model.

This holds true for USA-made Philco 38-116 sets. Canadian 38-C116 sets may differ in production code numbers.

Another thing about 38-116 sets. 38-116 Code 121 models used the 1937 RF unit (same as used on models 37-116, 37-675 and 37-690), with a multitude of adjustments. On the other hand, 38-116 Code 125 models used a different (new for 1938) RF unit with relatively few trimmer condensers. The later RF unit is the same one as used on model 38-690, code 125.

It just seems strange that they would do things that way, the usual pattern was to have an original version as a code 121, as they were in this case and most others, and then a code 122, and so on for subsequent versions, most models never went beyond two versions in a given production run from what I have encountered. I wonder why they would have skipped codes 122, 123, 124 and jumped straight to code 125? Unless the code numbers have nothing to do with what was actually produced and only to do with circuit designs? Maybe the 122-124 never left the drawing board? If you are talking about the Canadian built versions they could be different yet again, and often were since they often sourced parts and supplies locally. The only way to find out would be to talk to a Philco engineer who worked for the company between 1936-38 unless the records explaining why miraculously survived. This is one of the aspects of old radios that interests me, too many people get caught up on cabinet designs, I like to look in the back and beyond.
Regards
Arran