Only horse armor can be crafted, but horse equipment cannot be crafted. The reason why you see the signature on it is because those horse equipment are obtained by opening the cryptographic silver treasure box. They are all signed, so naturally the horse equipment is also signed. Horse equipment can also be obtained by killing monsters and bosses, but these do not come with signatures. The horse equipment can be dismantled. I tried it. I removed the unused shoes and got a horse armor fragment. The horse armor fragments that were dismantled were not as good as the signature horse armor equipment obtained by opening the box in terms of quantity and level. .