Tav #1. Tav, the final letter of the Hebrew alefbeit (alphabet). The picture behind tav is the sign or seal of a covenant. It was often used as a mark in the same sense as our signature is today, especially of those who could not read or write (similar to the practice of signing an “x” on a contract).
CONCLUSION
Honest Abe’s signature is unique and cannot be counterfeited without a skilled forgerer spending thousands of ours learning every curve and pen mark.