I can only speculate. This could well have contained a layered (with trays of parts) field repair kit for field armorers; A few years ago, one of our members acquired a complete armorer's kit.
There are photos of a couple of these kits on this site:
http://forum.lugerforum.com/showpost...94&postcount=5
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Igitur si vis pacem, para bellum -
- Therefore if you want peace, prepare for war.