There are a lot of experts out there, but the only sure way is to have Laurie Franklin authenticate it. There have been a ton of really good copies/forgeries out there. Also, it can be really tough to determine whether an early, legitimate cue is a SW or Kersenbrock, but you would not be a loser with either of those.
Joe
Hi Bama is right nothing beats a letter from Laurie.
If you don't have time to do that try this. Look at the tips of the points. With both SW and Prather points instead of having a glue line in the middle of the points one vaneer has a sharper angle and the other runs into it from the other side so the glue line is slightly off to one side. On most of the ripoffs I've seen the glue line is in the center and not nearly as clean.
Orion