2 for 1 on this post. What are they?

[Metal Illness]

Possible shell button? And some kind of tool for checking thicknesses? The tool thingy says "Pat Apd For" I'm guessing Patton Applied For and at each notch it says 10, 25, and 50. What is it?

 

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[yaxthri]

The shel thing looks like a button but the photo is too blurry to tell if there are marks of a removed attachment ring if so.

I think "patent applied for" is a better interpretation, anyway this is an interesting mystery tool thing.
I'd like to see what it's id will be... I have no idea

 

[DCMatt]

Spark plug gapper tool?

 

[Charlie P. (NY)]

If you look at the indexed metal disk the three cut-outs are gradually further from the center in a spiral. So I am guessing it was to control flow of something. Seeds or air or water flow. Odd the holes would be arc shaped and not just round. As it turns and goes to the next edge slot they would each face the same direction in turn. That has to be for a reason.

The shell is a button that didn't work out and was scrapped; my guess, anyhow.

 

[Tedyoh]

I like Charlie's control flow theory - maybe the slots on the side were the locking mechanism and the center triangular holes are shaft holes - part of a thumb operated spring loaded device maybe? Kind of like the bottom of an old powder flask. Pretty cool w/e it is.

 

[JRedHorse]

The shell is abalone and the other item is a feeler gage.