From what I can see these bases resemble typical commercial G&H bases with the ovolo sort of bevel below the dovetail. The one on the SMLE appears a bit longer. It is a very professional fitting job Roger. Does the rest of the rifle correspond to it in quality and fitting?
I wonder if either of these bases match the stock length of the commercial G&H bases?
I assume that their bases were sold as undrilled blanks by G&H, but the fact that so many of them have three equidistant screw holes and two locating pin holes in more or less the same location would suggest that they may have come that way from the factory, or else that G&H supplied three screws and two pins and a drawing suggesting such an installation.
Obviously that base on the SMLE was either custom made or came undrilled from the location of the screw holes.
Funny little fact about these G&H mounts is that they are often set much higher than they need to be on sporting rifles and it doesn't seem to have occurred to most gunsmiths that they could mill off the bottom edge to set the base as low as possible. G&H would of course have made them with extra depth to suit all possible applications.
A set of original instructions from the 30s would answer some questions.