Rick,
Yes a fowler is a shotgun. I use my Brown Bess to hunt Grouse. Most fowlers today are made using kits, you can buy a complete one. This one for sale by griaguns is a good deal. You would be hard pressed to buy the parts for $775 in MHO.
http://www.canadiangunnutz.com/forum/showthread.php?t=506998
You have what was originally a so called "Chief's Gun". These were distributed by the British Gov't. in connection with treaties. It has been converted from flint to percussion, and restocked, no doubt contemporary with use. Originally it would have had a silver thumbpiece with a bust of an Indian with bow and arrow.



























