The mounts are EAW copies and not made by EAW. This is per New England Custom Gun and one other source, that I don't remember who.
NECG claimed that one in ten of the EAW rings might fit the Winchester bases, but it would be dumb luck to get that the first try.
I tried a set of rings that Jeff,s Outfitters had, but they didn't come close to fitting a 7x57mm that I'd bought that was missing it's rings.
NECG can install a set of EAW mounts and rings, but were talking mucho dinero.
Mike, when you say the rifle is "drilled and tapped", I assume that the bases are missing as well.
Some of the Grand Europeans were made and sold without any bases and rings and also not drilled and tapped. I know because I have one of these in 9.3x74R. They were probably only those made for the European market.
Given the 7X64 that you have, it may have been one of these and someone had it drilled and tapped for a completely different mount than the EAW copies.
A good gunsmith could fit a set of Leupold Quick Detachable mounts for the rifle and they are as good, if not better than the EAW mounts. Not as complex, but every bit as sturdy.