Anyone know the specific use for this old feeler gauge set I found?

[Lump]

I hit a honey hole estate sale last weekend, and I'm trying to get some photos ready for GJ forum, but there is a lot of stuff and I have too many other projects pressing me at the moment. (I'll get that done shortly). But my curiosity has gotten the better of me regarding this unusual feeler gauge set which was in one of the boxes of automotive items I bought. Can anyone tell me the specific purpose for this set?

Each gauge is thicker or thinner, as the stenciled numbers suggest. But what are those slots for?

Thanks in advance.

 

[Cruzan80]

I have a set like these as well. But I think the numbers on mine aren't for feeler thickness (would have to check). Also interested in the "why".

 

[pancholasvegas]

These look like shims that would be used to position pieces - Similar to the shims used on older body panels for aligning fenders, etc.