Well, I couldn't resist so I bought the damn thing.
It came in a box sealed in a plastic bag. Writing on the bag is exactly this:
1005-722-3097
BAYONET-KNIFE, M6
1 EA.
DAFF 03-67-C-0069
A-
12/68
Inside the box, it was wrapped in a silver lined wrapper with a load of writing:
No. 505 V.P.I.
TYPE I & II, Class 2, Style C
MIL-P-3420B
The Original Volatile Corrosion Inhibitor
***(Instructions for use)***
Marvellum Laidloss <--- kinda difficult to read, the silver is flaking off
Holyoke,Massachusetts, U.S.A.
Licensed under Shell Developement Company
Pat. No. 2449962 and Pats. Pending
10-67
The bayonet itself has U.S.M6 on the left side of the handguard and Imperial on the right side. Both facing the knife edge, readable with bayonet lying on right side. The blade is black, black, black with a very fine edge ground completely around to the top flat. All other metal is black. No other markings. No rust and nothing really like oil or cosmoline to protect it, just the wrap.
This box contained one bayonet and no sheath. I tried to take pictures but my digital camera is crap and I'm sure you all have had enough of ruining your eyes on blurry pictures.
Should be authentic, yes/no?
Just wanted to add that there was a folded cardboard sheath around the blade on the outside of the silver wrap as well. No writing on it though.