I blew it up a bit, and adjusted the contrast so you can see it better.
It's there.
Clear tape was not *usually* used over the top of an area that would print.
It would have been taped around the sides with red tape (which blocks out the light from imaging the plate).
It could have been taped down to hold it in place, red tape placed on the sides, then the positioning tape removed and left some residue.
It just seems an odd place for tape to be laid by a stripper.
I'm not doubting that's what it is. It could be.