There are two elastic loops to hold the bayonet in position; one at the tip of the blade and one that goes around the grip. When properly inserted in the case the bayonet is quite secure.
Placing a value on a item like this is hard. There were not that many made. If someone was trying to assemble a complete collection of all M9s made and needed this one, they might be willing to pay a hefty price for it. Other collectors won't touch a commemorative if you were giving it away.
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