Scott C13 Question

I bought this as mint hinged and until I scanned it I never noticed what appears to me to be a cancel mark on the right perfs. Would anyone care to hazard an opinion on that? Thanks, yakboomer.

The little shaded mark on your c13 looks like marks left from tiny strips of adhesive..my father used these adhesive strips on those crystal mounts to keep the stamps in place and.over many years the stamps had stains like your c 13 stamp....anyways it sure ruined a lot of mint stamps...or maybe a cancel...?..oh and can anyone please tell me the way to remove self adhesive stamps from the paper..I have been gone from collecting for a long time....the old lick em stamp days..thank you...

Thanks SteveWb, as far as removing the self adhesive stamps from paper, I have had lousy luck in doing so, but if you do a search on it, I am sure you will find many posts. regards, yakboomer.