San Marino Scott #17.
While I find no mention of it being counterfeited, with a stamp of this value ($925.00 in the 2020 Scott for unused). It doesn't hurt to get a certificate for it to be sure.
The main problem you might encounter with a valuable stamp like this is it probably is genuine, but could have been a used (only $125.00 as used) stamp that had the cancel washed off, and then was regummed. One thing that might be in favor against that is if the stamp was printed with aniline ink. Most cleaning attempts would dissolve the ink.
re: San Marino
San Marino Scott #17.
While I find no mention of it being counterfeited, with a stamp of this value ($925.00 in the 2020 Scott for unused). It doesn't hurt to get a certificate for it to be sure.
The main problem you might encounter with a valuable stamp like this is it probably is genuine, but could have been a used (only $125.00 as used) stamp that had the cancel washed off, and then was regummed. One thing that might be in favor against that is if the stamp was printed with aniline ink. Most cleaning attempts would dissolve the ink.