If you plan on shooting it, make sure you find out. I'm sure you are aware, but if you shoot today's smokeless shells through it you could tear up the old gun and also hurt yourself. If it's from the 50's, I bet you are okay... but make sure to check first.
Here is video of me dusting a pheasant with my side by side 10 gauge from 1889. Took it out last year and shot it for the first time. Found a company to make me black powder shot shells for it... was a lot of fun. Check out how long that gun is towards the end of the video.