Louis, lovely rifle for sure. The scope bases are definitely British style. Exactly the same front base as a pre-war Rigby. Having said that, I have taken measurements from an original Rigby and the bases are all in nominal metric dimensions, meaning they were made in Germany for Rigby.

As the rear base has no hook or locking lever you would either need to modify it to accept a lever the same as the front, or the rear ring post height has to be such that it slightly springs the scope tube to place downward pressure on the rear ring. I would always opt for the first option.

Matt.