The value of a bayonet has a great deal to do with its condition and completeness. I can't see the blade which is critical. Any dents in the blade cutting edge, or a broken tip, will slash (no pun intended) the value. An ugly cutting edge that someone has sharpened with a file or grindstone is a curse. Rust pits are also bad news. A big detraction is a missing scabbard, and I don't see a scabbard in your pic. Bayonet collectors like their bayonets complete down to undented scabbard, frog with leather in good condition, with blade bright, smooth steel, and sharp, fully-legible markings if that's the way it came from the arsenal or factory.
I wouldn't pay too much for a bayonet that has many of the problems I mentioned, as it could be hard to sell.
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I collect fine cannon models, full-size antique cannons and artillery accouterments.