This is an unusual float where a bubble protrudes out of the seal.  I'll take the liberty of calling this float an 'Outie'.

I've seen lots of floats where the bubble gets sucked in and forms a 'double bubble'.  I've only seen a couple of these 'Outies'.

There is also a maker's mark that I haven't been able to identify.  It appears to be a simple Check Mark (upside down in the photo).  It's a clear and defined stamp but it's tiny.  The longest leg of the check mark measures approximately 1/4 of an inch.

This float measures 3 inches in diameter.

It's an authentic Japanese glass fishing float that was found in Northern Japan.