Folks:

I'm relatively new to the world of fine double shotguns and am a bit bewildered by some of the terminology. Can someone either explain or direct me to an explanation of the various classes of shotguns. For example, I inherited several nice doubles but I'm not sure whether they are sport, royal, best or some other designation I've heard mentioned. Two are Francottes bought from Abercrombie & Fitch back in the day. Both of these guns have very nice engraving but I don't know if that puts them in a certain class or category or not. Likewise, are all Purdey doubles "best" guns or are there various classes within the group of doubles? If so, how does one tell? By the type of engraving or is there a mark somewhere on the barrel indicating what class the gun is.

I'm sure it's apparent that I'm clueless and I would be happy to read up on this but I'm just not sure where to start. Any help in pointing me in the right direction would be greatly appreciated.