This is a modern float made directly by Saiichiro Asahara, a 4th generation Asahara float maker.  He produces glass floats with all the original molds and methods of his ancestors.  

Saiichiro made this 6 inch glass float at his factory in the city of Otaru on Hokkaido Island, Japan.

Although the Asahara Glass Company didn't traditionally use maker's mark when they were producing glass floats for commercial fishing industry; Saiichiro now uses his own a maker's mark.

It's distinctive box shaped stamp with the symbol Asai 浅 inside which means shallow.  I'm assuming the mark is 'Seihoke Asai'.

These 'authentic modern' floats are not seen listed on eBay very often.