This is going to sound funny about a tool as simple and as innocuous as a carbon scraper, but I also found what might be my best find of the year so far in 2020 at the same place.
These tools were part of the pre-war and very early war (No 1938 to Nov 1942) Motor Vehicle Mechanics Tool-Set. They were used to clean piston, cylinder heads, valves, and other related parts that tend to build up carbon. They were dropped after that, but could still be found in the Master Mechanics Tool-Set, which was kept in the sidebox on the back of a Dodge light wrecker.
The ends of the wires are chamfered on the end and as you might know or suspect intuitively from the design, they conform to any shape, and can be made more rigid or more flexible with that little sliding band.
They are not exactly rare, as a category, and I've found many over the years for my GMTK's, including Blue-Point (their model number ws cited as a spec in ORD 5 SNL J-4, 4 March 1945), Wilde, and Plomb, as well as a bunch of unbranded examples. My theory is they were all made by one company (probably Decker).
But, I've never even
seen a Duro-Indestro and didn't really know they existed. On top of that, even though we tend to refer to Duro-Chrome and Indestro as "Duro-Indestro", and the conjunction is further implied by the "-D-I-" markings suspected to indicate such a conjunction, it is the only tool I have ever seen let alone found that was explicitly marked as such. If someone knows of another, please disabuse me of this notion.