Older S&G indirect vault lock info?

[Riyame]

Hello,

I recently received this S&G vault lock and was wondering if anybody could help me date it and any other info and possibly help me find a change key and possibly a new dial ring since mine has 2 threaded holes in the side.

From what I have seen on S&G website with the U11 change key, it only works on locks made after 1956. I assume that is due to the plate that is behind the back cover with the change key hole.

My lock does not have this plate but it does have a change key hole in the back cover. The gears of the indirect drive are also open, unlike the newer locks. It is a 4 wheel model.

Sorry for the poor pictures. Thank you for any help you can provide.