They were using Roman numerals. It's true that with Roman numerals and writing out the number using words, it's harder to forge. See https://m.reddit.com/r/AskH

They were using Roman numerals. It's true that with Roman numerals and writing out the number using words, it's harder to forge. See https://m.reddit.com/r/AskHistorians/comments/49z4d6/why_did_florence_ban_hinduarabic_numerals_in_1299/ https://m.reddit.com/r/AskHistorians/comments/49z4d6/why_did...