Here's a picture from Gene Gangarosa's "Spanish Handguns", showing the date codes assigned to guns by the Spanish proof-house; these codes will be found as a letter (sometimes a letter and number) next to the main proof on the frame (which looks like a shield with crossed rifles in it). So, if your pistol has a "Q1" next to this proof, it left the factory in 1972, and so on. Hope this helps.
