How can you tell if a prop as already been labbed?

They charge you a lot for it. LOL.

I would imagine that if the prop were labbed in the aftermarket, the person selling the prop would have a reciept as proof of the work. In the OEM market, I believe that Mercury Marine stamps an 'L' on the prop when it has been labbed. Can anyone verify this? I seem to remember something about that.

take 3 measurements of blade thickness from the base to the tip.... you want......i would have to kill ya....check with the apba for the specs of stock props.