Calling all smarty-pants!

I know this is a stretch but I've been rebuilding a b18a/b motor- took it out of the car and started taking it apart and noticed this gasket on the floor. Not even positive its from the motor but guessing it is.
It is silicone around a very thin metal washer. It is about the size of a quarter and is pretty much flat.
I've started reassembling and havent found anything that seems like it needs a gasket and i've looked through the helms a few times- growing increasingly more and more freaked out.

Anyone? Please?

 

The engine was not open so it couldnt be from inside. Its not an OEM gasket. I vote for axle seal.

 

Im not sure at which point of engine breakdown I was in- think the head was off and i could have had oil pan off and been working on bottom- i have no memory of it really.
Not sure what you mean by axle seal as this thing is tiny and flimsy- it looks like the only area it would be safe would be inside the motor somewhere.
The only thing it comes close to in my mind is a oil pump seal- but thats an o-ring and it was slightly too small for that anyway.
Size - its smaller that the small end of a camshaft-but it will fit over the threaded receiver on the motor for the oil filter

 

It is not an axel seal.

Axel seals...

40x62x8mm.94