For whatever it's worth, there are two Hollenbeck drillings listed for sale by Cherry's Fine Guns in Greensboro, NC that are factory chambered in 30/30 Winchester, although both are a bit rough and in need of work in my opinion. I don't own a Hollenbeck drilling yet; but do own a couple of his more uncommon side x sides; one is #28 an un-graded 12-bore for which no records exist (as with #35), and the other #412 an A-Grade 12-bore with the Wheeling, West VA address but marked Three Barrel Gun Co. Although a fairly early serial number, #412 was not shipped until 8/15/1908 when it was shipped to Morgan Bros (whoever that company may be?). From the surviving records it seems that all Hollenbeck and Three Barrel marked guns were numbered consecutively so that serial numbers for drillings and side x sides were intermixed. Although I know zero regarding the history of gun #28, I feel confident that the hands of Frank A. Hollenbeck himself touched that gun many times during its manufacture; and feel that the same is true for your gun #35.
