I'm VERY familiar with Harder... Owego, NY, Athens, PA, Waverly, NY, then Lock Haven, PA. My nephew owns two Harders. Both have the semi-perch belly but neither is similar enough to the gun we see in the OP for me to even remotely connect Harder with this rifle. It would appear that Harders could be expected to have a less elaborate trigger guard and a fair smattering of inlays while this gun does not. Harder did, however, use commercially available furniture and upgraded it with attractive engraving. All of which combined to make for a rather unattractive (in my opinion) but expensive gun. For the record both Harders were combination rifle and smooth bore guns.
As to being a PA rifle, I think probably not. (I said "probably" as by the time this rifle was manufactured much of what was once local influence was being lost.) Years ago we had almost the same conversation about another similar rifle which turned up in the Adirondacks. Speculation was that it was a Mohawk Valley gun made somewhere between Albany and Rome. It turned out to be a commercial (trade) gun sold by a sporting goods establishment in NY City. This is not to imply a cheap gun as it was anything but. I believe it was eventually determined to have been somewhat of a kit gun using British components and finished in what we might think of as the store's custom shop.
