Colt marked M7 quite curious

[Misfit-45]

Hi,
Did you see the colt marked m7 on ebay? 121044811428 Very similar to the Imperial/Colt M7, but it has a 90 degree back cut.
It also has a star burst peen like the WWII M4 bayonet.
Where does this bayonet fit in the scheme of things?
I also asked the seller if he would remove the handles to see if the cross guard was secured by a "U" shaped piece of metal and he said it was.
I thought I might bid up to $150, but it went for $252.
Any opinions?
Marv