Day first saw a part of it peeking up on the barrel as the barrel sat in the wooden stock. When Day removed the barrel from the stock, he saw that much more of that same print was underneath the barrel ("Off Underside"). Pretty straight forward, if you ask me.
Thank you for posting the pictures of the carcano stock,and barrel. It's a shame that you couldn't have supported your argument by posting a picture of the INSIDE ( barrel side) of the wooden stock. Because if you could see the inside of the stock at the bayonet lug then you'd know that there is NOTHING on the barrel that would create what you have pointed out as
"POSSIBLE MARK FROM BAYONET LOCK OR TAPE EDGES"There is no place on the inside of the stock or the metal barrel at the foregrip that looks like the photo of the "palm print" (CE 639) on the 3 X 5 Index card.
CE 639 ... The palm print...CE 2003 Volume 24...page 260
It's nice to see that you believe the print was lifted from the bottom side of the WOODEN foregrip, Where the slot for the folded bayonet blade is cut into the wooden foregrip. ( though you attempt to obfuscate that fact by writing
"Possible mark from bayonet lock or tape edges" That slot is clearly visible in the photo (CE 639). and can be measured by scaling the photo (The Card measures 3" X 5") The bayonet blade slot measures 3/16" across and it extends about 2 1/2 inches to the rear of the Bayonet lug. It's obvious that the "palm print" lift was lifted off the bottom of WOODEN foregrip.