I overpaid for this... IBM Model M ashtray, for the lack of a better word. I looked at pictures of the internal assembly online, and I think there're missing springs? For example, I can't press the upper half of the enter key because there's just no spring there, not even blue placeholders. I can't exactly buy new springs from Unicomp as the shipping is so prohibitively expensive that I could buy a IBM Model M from someone else.
It's the ISO enter key with stabilizer judging by that image.
But I found an interesting reference that suggests that everything here works as intended.
Image 1: 122-key IBM Model M
This layout matches mine with the following exceptions:
Image 2: 122-key IBM Model M internal assembly
If you look at the placement of stabilizer inserts, then this matches my IBM Model M. Same exceptions apply. I couldn't determine whether the 122-key IBM Model M enter key also uses a stabilizer metal bar, but it's suspiciously similar to my layout nonetheless.