I shoot the heck out of mine! It's the best darn SASS rifle I've ever shot. Mine was imported by Cimarron Arms. It has the 24" octagon barrel, color-cased receiver and lever, and a straight gripped non-checkered stock. Don't know if it's RARE, but I do know I haven't seen many in that caliber, most are carbines. I snapped it up the moment I saw it on the dealer rack. I've got a brace of .44 special Colt's that I shoot matches with and this rifle is the cats pajamas to team them up with.
I'll assume that you are planning on keeping that '73 you acquired, but if not...drop me a line, I might know someone interested in it.