Measuring a used piston

I recently did a top end job on my 97 YZ 250. I changed it out because I do this once a year.   The year old piston was a Weisco. It appears to have done very well. There is a slight polishing on the intake side. EVERYTHING else on it looks brand new.

I had allready bought a new kit, so I put the new parts in.

 

My question is this. The service manual lists the dimensions for the stock piston and the wear limits. I hate to keep this old piston around if it is worn out, but have no idea as to how to measure the thing or what to look for. I would also liek to know if I wasted my money changing it out.

 

Thanks for any help on thsi !

Steve, I thought about that right after I posted.

I took the lazy way out thinking..."The coating is still there, how worn could it be?"

Yea, I should be forced to kickstart a YZ 490 in flip-flops for not doing that!