I think you are pretty close...the AR is artillery regiment. And its first battery; which is a company sized unit in the artillery.
A gun in the condition you describe is not heavily sought by collectors, but it is still a bona fide piece of history. Pls do not futz with trying to make it shiney. I'd guess the value to be between $500-550
Tom A <img src="graemlins/xyxwave.gif" border="0" alt="[bigbye]" />