Czech VZ-24 bayonet
Most Czechoslovakian Mauser bayonets had inverted blades (sharp edge on top, the same side as the muzzle ring), like the AK and Austrian M1895 bayonets.
I didn’t measure this one when I saw it in a pawn shop in Bolivar (pronounced “bolliver”), Missouri, but with a blade length just over twice the handle length I must assume this is a 30 cm bladed VZ-24. The VZ-22 knife bayonet had a 25 cm long blade, copied from the Austrian M1895, and the VZ-23 sword bayonet had a 40 cm blade.
The CSZ initials over the B on the left side of the ricasso are a dead giveaway that this is Czechoslovakian, probably either pre-WWII or post-WWII but before the communists started marking them differently in 1948 or so.
These bayonets were made to fit on the VZ-23 and VZ-24 rifles. During WWII, the Nazis forced the Czechoslovakians to make them for the Mausers of their Romanian allies. Czech bayonets made during the German occupation had number designations, rather than the CSZ initials, in addition to other modifications.
The serial number is on the pommel below the mortise.
A definitive source for information on Czechoslovakian Mausers and their bayonets is Jan Šmid’s 2016 book, Pušky a Bodáky Vz. 24, although a more concise and easier to reference source is worldbayonets.com’s Bayonets of Czechoslovakia.