My grandfather gave me 3 of his shotguns this weekend.  They are all break open guns.  One of them looks like it would be a black power shotgun.  There is not much of anything stamped on the barrel.  One has a company i've never heard of, one is from sears roebuck, and they all have the gauge on them.  If I take off the wooden stock under the gun and remove the barrel I see random numbers in different spots.  I see no serial numbers.  Is there a gun book I could buy or rent from the library that I can use to identify exactly what I have?  Also I doubt I could shoot any of these without replacing the o-rings.  They were used frequently for hunting plus they look pretty old.   
I took a picture with my cell phone of all 3 guns together but I don't know if that will help.  I can link that if it helps.