Info request

Of the firearms I inherited from my deceased father, there's one I'm not entirely familiar with and would appreciate any insight this forum might provide. While I'm not necessarily looking to sell it, I'd like to know if I can find an approximate age and value. It's a Marlin 12ga pump action w/exposed hammer; serial number is 45517. Besides being well used & worn, it's sat for as long as I can remember untouched in the gun cabinet. Sorry for the quality of the photos. Thanks in advance for any information you might have.