Just checked, and the NSN matches the canopy for the MK4 Inter. Admittedly, its hand-written at the bottom of page 234 of the MK4 RPS that I have, but all of the other manually added info in there has been right so far.
Someone certainly scored a bargain, if its in usable condition. Even if it was rotted or the stitching was going, it would make a good template.