Looks like a early Yellow Aircraft A-Fo to me.

You might want to PM Buck (Yeahbaby), he was flying one of those about 6 months ago and probably will be able to help you with CG and throws.

That damage in the spinner could have been caused by a probe slipping. Triple check to see if a 1/4" ball end allen will fit it. It is possible that someone changed it out, but they probably would have had to machine a new fan nut to make it work with a metric bolt. I think it is very unlikely that someone would go to that much trouble.