Sorry I tried 2 times...I thought it would show up after a while, as it happens sometimes when listing items! /Users/jacquesfamery/Desktop/SCAN/612?.jpeg
It's the lower of two values celebrating Yugoslav monuments, issued June 9, 1983. Scott #'s 1635-1636. Both stamps show two perforation varieties: 13-1/2 and 12-1/2.
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https://www.hipstamp.com/listing/yugoslavia-1971-sc-xx-o-used-single-stamp/30324215
Hope this will work!