I have never known a scope number to be duplicated, never, ever. But I ain't seen 'em all! I have seen some/many with the number over engraved as though to highlight an indistinct number including one where the old number was still(?) partially visible and the new number was over engraved as 23xxx instead of 25xxx. So on that basis, 23xxx COULD be duplicated. like I say, we never obliterated numbers as this usually leads to suspicions and questions.