OK - kept looking. I knew I had seen one before -
It's a 6x2 bayonet for the AK47.
This appears to be a Bulgarian version - brown bakelite type handles and a flat lip around the tip of the sheath with serial numbers on the pommel but perpendicular to the spine.
The East German versions had black handles.
The Polish versions have sheaths with no flat lip around the tip.
The Russian versions look like the Bulgarian version, but the serial numbers on the Russian versions "typically" run at a 45 degree angle to the spine.
Edit to add - In general, AK47 bayonets are typically a dime a dozen on fleabay - they go anywhere from $15 to $80 depending on condition, presence or absence of the sheath, presence or absence of the belt dangler. Some folks tag a big price on them claiming they are "rare", but those sit there for weeks at a time and seldom sell.
6x2 bayonets are not as frequently available on fleabay, but the last 3 have gone for
$"some best offer accepted" below the $89 asking price.
The first 2 were similar to yours, obviously carried and missing the dangler. The 3rd one was nearly pristine with the dangler.
If I were bidding on it on fleabay. my max would be $40, preferring to get if for less.