This will fit the Model 1842 muskets, but really was made as a replacement for the earlier converted muskets, and is called the US Model 1835 socket bayonet. Here is a listing from Tim Prince's fine website showing one of these:
Rare "Crossed Arrows" Marked US Model 1835 Socket Bayonet
collegehillarsenal.com
Tim writes that it is a rare variant.
I also would remind you to remove that bayonet from your bedding before turning in for the night.