That is a Pennsylvania National Guard pistol marksman medal. If memory is correct, it's for one year, multiple awards for subsequent years would be designated by the corresponding change in the number. The design changed quite a bit before they were standardized. I've attached a couple of examples. Here's the contact info for the First Troop of Philadelphia-
The Armory 22 South 23rd Street Philadelphia, PA 19103
telephone: 215-564-1488
e-mail:
adjutant@firsttroop.com