You could start by searching this forum using the Search Bar at the top of this page. A quick search for "Hollenbeck" provided 200 results. Many of them deal with the Drillings:
You could also search for the two successor companies that were formed after Hollenbeck reorganized... "The Three Barrel Gun Co." of Morgantown W. Va., and "The Royal Gun Co." of Wheeling, W. Va.
They are interesting guns, and fairly seldom seen. I still regret not buying a nice 12 ga. x 12 ga. x .30-30 Drilling made by The Three Barrel Gun Co. I used the money I had at the that PGCA Gun Show to buy a VH Grade Parker instead. It didn't have much engraving, but was in high condition.
