I wish I had some earlier signatures to compare. These are (if genuine) early ones I think. The later ones I posted are almost a shorthand of the earlier ones. If you are signing hundreds or thousands of books, your signature is not going to stay identical and if these are genuine, they are rather more complex than the later ones.
It's possible that Colin Smythe
, Terry's agent, may be able to give you a definitive answer. Personally,I'm inclined to think they are genuine - but who knows?