Mine has a 25AP22A
Here's the data sheet, scroll down for dimensions.
Aspect ratio though, is 19.844/15.562 = 1.28, which is consistent with my set, and also with your ideas about TVs being slightly narrower than 4x3. Also, if you think about it from test patterns and such, it does always seem like more is cut off on the sides than on the top and bottom. This is a typical CRT size, the 25XP22A in my RCA CTC38 has the same dimensions, and that's a tube TV. Makes me wonder about other brands.
https://frank.pocnet.net/sheets/202/2/25AP22.pdf