Looking at a 228 that is stamped "Made in West Germany". Are the older guns stamped like this? How can I find it's age?

Underneath the front section of the slide should be some proofmarks and two letters. The two letters represent the last two digits of the year of manufacture. Here is the letter to year code used by SIG:

A = 0
B = 1
C = 2
D = 3
E = 4
F = 5
G = 6
H = 7
J = 8
K = 9

So a 228 with a letter combination of "KJ" would mean the pistol was made in 1998. A letter combination of "AC" would equal 2002 and so on.

Many thanks