I am fairly sure it was the same Harbour Master for Porto Montenegro,  at the Tivat customs dock who readily accepted our Florida boater "license".  She squinted to read the numbers, those little zeros on Mark's sample card. Worked later on in Cavtat, Croatia as well and some island I can't remember in Greece.

We also carry a special universal set of special permision items for harbour masters (Albania), military and coast guard boarders (Morocco), berthing requests (Italy, Gozo and 2 month Covid lock-down in Colombia), and workmen who we want to give us fair rates or better service (Turkey and Tunisia).  Seems to be universally accepted and you don't have to worry about pesky translation problems.     https://photos.app.goo.gl/9499u2EgwRqyffAP6

Somewhat related, we always stamp the sales receipts and even boxes for items we are bringing through customs (self inker $10 on eBay) and we include a stamped color 2-sided copy of our USCG Document in each suitcase that have items and boat parts  https://photos.app.goo.gl/MgRpPdEBBjNbySV57 

No guarantee but so far 23 countries, no problems.

Cheers, 
Bob     KAIMI SM429