I'm guessing it may have come from a German mobile shop truck. An article from the October 1943 issue of Ordnance Digest, published monthly by the Ordnance Department of the U.S. Army, describes the German mobile shop trucks and how certain features of these units compare with similar ones in use by our Army. Quotes from the article based on equipment captured in Africa state:
In the mobile machine shop truck, the hand tools were stored in recessed wooden drawers, similar to those in the electric repair truck. These hand tools included such types as pullers, valve refacers, body repair tools, punches, and wrenches. While the hand tools did not consist of a large variety of different classes of tools, they did include a large assortment within certain categories. As an example, expansion reamers covered sizes from 4 mm to 52 mm. In some cases extra sets of taps and dies were calibrated in inches rather than in millimeters.
An extract from a report from the North African Theater of Operations states ". . . of particular note are the quantities of precision instruments (gages, star gages, micrometers, etc.) which are made available as standard equipment (in German mobile shops), and the arrangement of all tools and parts drawers to provide fitting compartments for each type and kind of item. Also highly worthy of note are the chests provided for each type of weapon, containing special tools and small spare parts. Another thing that caught attention is the locked compartment for tools for the maintenance of the vehicle itself, providing fitted drawers for the tools and including spare spark plugs, fuzes, and other small emergency items . . ."
Lists of equipment and maintenance manuals were found in the electric repair truck and also in the machine shop truck. These lists are now being translated for further study.
In general, the pattern of the German mobile shop trucks follows that of the United States Army mobile shops.
Just a thought and I hope this helps!