I recently acquired several NOS Jaeger single-lever side mounts with blank bases plus a number of spare blank bases. Apparently these are the last remaining stock of the Jaeger firm/name when they quit their business in TN but I'm not sure of the details.
These mounts are all brand new, never been on a rifle, and none of the dovetails, NONE OF THEM, are interchangeable with one another. They show the usual bell curve distribution, a couple being larger and smaller while the rest fall somewhere in the middle. Only a few thousandths difference between most of them, but it's enough to notice. Here's a photo of the two types of bases I received, the top one is already machined on its back side for the large ring of a Mauser while the other is left thick & flat & long for fitting to anything including a Mannlicher-Schoenauer.
The point of this post is that I have enough spare blank bases so that the odds are good that I can find one to fit an orphan mount even if it's a G&H. Similarly with the mounts, I sent Jerry a couple of different-sized Jaeger mounts to try on his G&H base and we'll see how they fit. He has my smallest and my largest, so if his base falls somewhere in between them then I can probably match it and he'll be in business. We'll see.