Depends. Most earlier ones were completely made in W.Germany or Germany. Those are the easiest to determine. Goes like this: at the front end of the slide, directly opposite from the front sight, check for proof marks and a date code stamping. They look like this....
These decode like this:
A = 0
B = 1
C = 2
D = 3
E = 4
F = 5
G = 6
H = 7
J = 8
K = 9
My P228 (pictured) is a KH = 97 = 1997
The proof marks can be decoded here: https://store.bluebookinc.com/Info/P...Proofmarks.pdf
Another way is to check the inside of the plastic grip panels. There is a molded calander stamp of the manufacture date, it looks kinda like a clock.
The example pictured (not mine) shows a manufacture date of July 1990. If there were German parts and it was assembled in the US or is of more recent manufacture, the proof marks and date code stamping may not be there.
In the case of the P232, the proof marks and date code stamps are on the right side of the frame just above the trigger guard. There is also an unofficial compilation of manufacture dates based on serial number but I cannot verify the validity of the list. If you want it, I can e-mail it to you if you haven't dated your SiG's with the above information.