Hi Olivier,
The 11-digit number (
5180-698-7964) handwritten on the paper tag is a Federal Stock Number from
no earlier than 1949. Prior to that (and technically, even some time after that, up until 1953 when there were still overlapping federal supply systems in use), a stock tag or the item itself would've had a Federal Stock Number in an alphanumeric format used since 1934, and all through WWII, that included a phonetic letter in the middle to classify the tool (e.g., 41-P-7964).
While there is zero doubt that the tag was filled out and affixed to the kit sometime after 1949 (and again, more likely after 1953), the kit itself
may be older. It
may have been tagged when it was restocked or repacked as surplus. However, in my experience, most of the wartime tools and other equipment repacked in the early 1950's and sold as surplus in surplus stores had the older FSN's on them. WWII collectors are already leery of early 1950's repacks, because some of them also include tools that were made in the late 1940's. Which puts the onus on the collector to identify the item inside the packaging as wartime production by its features.
As others have indicated, your fantastic kit sure looks like the kit shown in the Independent Pneumatic Tool Co (Thor) catalog #38-A (dated December 1945) that Ole Slewfoot linked above.
You may be delighted to know that I happen to have Thor catalog #38 dated May 1944, and it includes the same exact kit. See pics.
Do the model numbers on the units match the model numbers in the catalog? According to the catalog, the units have model numbers G-1, G-3, G-4, G-5, G-6, G-7 and G-8. (The kit model number was G-9.)
Some of the numbers on the metallic or foil tags are illegible in the photos. If you transcribe all the numbers you can find on the kit pieces here in a post, there may be something else we can use to definitize the year of production. Such as a contract number, which often embedded a year. Another number that can sometimes be useful in cases like this is the serial number. But typically in cases where the item is very popular and a group of collectors have done some deeper research based on company records or other empirical data. That may be the case with Thor if you can find a good forum (such as Vintage Machinery, posted by woody above).
Or you could just wing it!
Given your location (the former ETO), the 1949 FSN on that tag, and it seemingly matching in appearance to a wartime catalog, the probabilities of this being military are very high, and the possibilities of it being wartime, or at least Occupied, are just as high.
Wartime collectors are a funny bunch, waffling between very hard and very liberal in interpretation, usually dependent on whether it's their tool or not!
If it was mine, I know I would be calling it wartime!
Nice find.