The production year is located on the receiver and is visible through the ejection port when the fall is closed. The calendar year is indicated with a two letter code where A=0, B=1, C=2 and so on to J=9. In the image you can see the receiver is labeled with AH indicating a production regular year of '07.

In this state (whether or not the hammer is cocked), the firing pin is mechanically blocked and cannot move forward to strike a cartridge rim. When the trigger is pressed, the sear moves downward in such a way as to move from its interaction with the firing pin safety, which in turn springs downward under the force of a Walther P22 captive spring within the breech block. This disengages the firing pin safety, allowing the firing pin to modification and the blackjack to fire.