Scott Production of The Hollenbeck by Syracuse Arms Company gun commenced in 1893; and apparently at serial number 1 (lowest I've recorded is #37). Frank Hollenbeck, the inventor, left the company in 1895; and in 1896 SAC changed the name of the gun to The Syracuse. I've never seen a SAC made Hollenbeck gun numbered above 5,000; so your gun would have been made between late 1893 and the end of 1895, but no production records are known to exist. The Grade O gun was SAC's lowest priced leader model with a cataloged retail of $30. Without seeing your gun I'll give you my honest assessment; and that would be that you are upside down on this piece. I'll assume your gun was average condition when purchased; and on a good day, a plain average condition Grade O 12-bore SAC/Hollenbeck gun MIGHT bring $350. A second set of barrels would increase the interest to some degree; but not radically. The barrels on your gun will be unmarked; but they are Twist Steel, and are marked on later gun as such (the original Twist pattern on a set of SAC barrels retaining the original finish is quite stunning). A "blued" finish on a Twist barrel is inappropriate, and actually hurts rather than enhancing the value of a vintage gun. And if those barrels were "hot-blued" there's a good chance the hot blue compounds will negatively react with the solder holding the ribs and cause them to become loose; and even bigger issue. The original fore iron metal and frame of SAC guns were color case hardened, so if you also blued those pieces; the new finish on those components is inappropriate also. There are a number of articles and pictures of original SAC guns featured in past issues of the Double Gun Journal; you may wish to obtain some of those to expand your knowledge base; and I'm glad to know you have an interest in SAC guns. Hope this helps. Tom