I think that every Adolph mount is different many have the holes on just one side. I'll look and see what I have. I've also seen holes like this on the mount that was made much later in Boston but can't think of the name. It's more then likley the one that was on the Remington 30.

I think it's G.N Albree the mounts went under the name Mon-O-Mount and Twin Mon-O-Mount.

MP Sadly Deceased as of 2/17/2014