D.H. Hilliard underhammer

I have an antique firearm I can find very little information on. I expect it is probably pretty rare up here in Canada. It's a D.H. Hilliard underhammer buggy gun made somewhere between 1830 and 1877 in Cornish New Hampshire as near as I could find out. It says D.H. Hilliard Cornish N.H. on the barrel.
It's a .54 smoothbore. It is perfectly functional and I have fired it many times with patched round ball or carded shot over the years. Major parts are all serial numbered and are matching numbers. Only defect is a cracked weld on the one ram rod tube to barrel, cracked only on one side. Really shoots great still! I'd love to know more about it but have never been able to find another one exactly like it on the internet. I saw one very similar once but the barrel was several inches shorter. Can anyone tell me anything about it?
Al

Very nice and what fun!

Very nice and somewhat unusual in being a smoothbore. Is that the original ram rod? Ingenious method of stopping it from sliding back. I hadn't seen that before.

As far as I can tell the ramrod is original. It's the oldest Firearm I own. I can't believe how nice the bore is. It has some very fine pitting but nothing major at all. A friend of mine originally bought it in British Columbia and then I ended up with it.

The full text of "American Gun makers including Supplement of AMerican gun makers", available on the web says this:

"HILLIARD, D. H.”” Cornish, N. H., about 1860-1880. Maker of an
under-hammer, muzzle-loading, percussion sporting rifle."

"AMERICAN FIREARMS MAKERS" by A. Merwyn Carey, ©1953, on page 54 says:

Hilliard,D.H. 1842-1877. Maker of percussion underhammer pistols, rifles and shotguns at Cornish, New Hampshire. He was active 1842 to 1877, and his son, George C. Hilliard carried on the business from 1877 to 1880."

Thanks! Some good information there!
Al

Very nice underhammer. What is it about these that makes them so darned intriguing. That .54 smooth barrel or roughly 28 gauge essentially duplicates the bore size of many of the "Northwest Trade Guns/Fusils" that saw so much use north of the 49th Parallel.