Well, it is a right-handed and percussion (I am left-handed, which is why I rarely shoot my other muzzle loader, a flintlock). The slats are a full inch across, and the barrel is rifled with 8 lands and grooves and a much slower twist than is readily evident to the naked eye. The serial number is in the low 4000 range (forgive my withholding of the full number) and does not contain any letters, just the 4 digits. It is a Renegade stock with the flat butt and no patchbox. There are two screws in the tang, and I have accordingly looked into adding a tang sight, most likely a Williams peep to complement the one on my .45/70.
I doubt very highly that the barrel is after market. There is an entry for this model in my father's copy of the 2000 edition of the Gun Trader's Guide, but it was little more than a cursory description and did not go into details as to the barrel twist and years of manufacture, and he has not located his cashe of older Thompson catalogues, lost to the happy abyss that is his reloading shop. Thompson does mention the Big Boar on their site, but most often in lists of models that certain accessories will fit and I have not been able to find a description of the retired model on their site.
The right-side barrel markings read:
THOMPSON | CENTER ARMS
ROCHESTER, NEW HAMPSHIRE
.58 CAL. BIG BOAR
I would provide a picture, but I do not have a digital camera at my immediate disposal. There is a drawing of a hog's head between .58 CAL. and BOG BOAR and the O is octagonal with the inner circle being circular and rifled.
My searching over the internet did produce a picture that someone else took of their Big Boar, and this is clearly the weapon I own:
As I mentioned before, my expertise is in cartridge arms. I work at a well-known sporting goods store as the local guru of gun trivia and strangely enough, the go-to guy for muzzleloading questions because West Texas is not a part of the country with a separate muzzleloading season or a large number of black powder enthusiasts. Part of my job involves appraising used guns to purchase on behalf of my store. Sadly, we only buy cartridge arms and I have no resources on hand to determine a rough market value of my new toy, but I knew very well that this rifle was conservatively worth $200. I was well aware at the time of purchase that I was not purchasing a vintage piece, but was instead holding in my hands something that would be immensely fun to hunt pigs with, providing I could secure a source of ammo, which I have. I am particularly curious as to the relative age of the piece because I at first estimated its age to be no more than 15 years, but my father had a suspicion that he expressed simply as "early '80s".