Does the back of the Certificate of Origin need to be signed when a kit changes owner

[MTSCustoms]

Hi all. Like the title says, does the Certificate of origin need to be signed on the back by the original purchaser or will the bill of sale be all I need? We didn't originally have the seller sign the back because it says for a dealer I believe...

Titling in NH if that matters, bought the unbuilt kit from the original owner in MA.

Thank you