Very interesting!  Canada FX137a - 8c on 5c, Printers Freak - Ink Fingerprint on front of stamp.  Usually a fingerprint will 
de-value a stamp because it is a collector's poor handling on the gum side.  However, this error is from the day that the sheet was printed, and it is the printer or the printer's helper's fingerprint on the front of the stamp.
These stamps were issued without gum because the cigarette companies that used these stamps used a machine to cut the sheets and then apply gum before they were placed on the packages.  Gum had to be absent because it would jam the machine if they were already gummed.