1. On the front of the rule the seller is given as MDS (Foreign). In the wood on the back the word Germany is blind stamped.
2. The extensions to the A and D scales, going as they do right up to the end of the rule, would have been almost useless.
3. The back of the slide has S, ST and T scales rather than S, T and L scales.
4. I suspect that the original maker was Castell as they used Mahogany on some of their rules and their Rietz pattern had the same configuration of trig scales.

Front view

Detail - front left

Detail - Seller