It may not work. Better get a fingerprint. It'll definitely work. Handprints are the only ones that are not easy to forge. Personal seals are easily forged. If the borrower and guarantor didn't admit it at that time, it would be very troublesome for you to prove that the seal was stamped by yourself with evidence. If we ask them to sign again, it will definitely be effective, and the signature is unique and not easy to be forged. If you still don't understand, please ask questions in time.