Chris,
Thank you for posting more photos. Great stuff!
The trigger guard is made from horn, not uncommon at the time. If it has a forend tip, it too might be horn. Shine a bright light on it or take it outside into the direct sunlight. It will look like layers similar to the trigger guard, which is how a piece of horn is made, by building up layers over the years of growth.
The latch on the left side of the stock is a lock to hold the bolt down so that it can't be opened accidentally by bushes or tree branches. The stock is designed for iron sights and the receiver still has the charger hump for stripper clips and the thumb notch. This just means that it is not one of the later solid left sided commercial receivers. Many of the civilian rifles were set up this way.
The cartridge was introduced by RWS in 1938 or 39 but was developed by Schuler a bit earlier.
One more photo favor... Could you show the full rifle from either side? You say that the stock is 3/4 length and I'd like to see if it is one of the African style rifles.
Thanks again for the photos.
Regards.
