I have seen an asparagus tractor (ac-B) on Ebay. It went for $4,000. It needed to be sanded and painted. ITn was pretty good though and ran good. They are rare! never even heard of a potato version. They are similiar to the farmall a and b in the appearance of the wheels to the bottom of the fram not above that incase you have not seen one.
The top looks like a regular B.