Were there others?
Yes, very probably. It has been observed that on close examination of the mechanism there is no evidence of any mistakes. All the mechanical features have a purpose. There are no extra holes, or bits of metalwork to suggest that the manufacturer modified his design as he built the mechanism. This leads to the conclusion that he must have built a number of predecessors. However, we don't know if he was the first in a tradition of makers, or the last. It has been suggested that the number of such mechanisms may have numbered in 10's, and at least some of these should demonstrate an evolution of design.