This is a prop that I got with a used motor that I bought. It is a Gen-U-Whine Yamaha as far as I can tell. Stamped 15M and 14-1/2 x 15.
 
It was in almost too good condition when I got it, paint all fresh and minty and no dings or dents. Anyways after running about 50 miles and never breaking 4500RPM I never noticed anything until we pulled the boat...
 
 
 
 
 
 
 
 
I swear I didn't hit anything and the last blade with it's tip hanging on by a thread doesn't show any impact damage. Anyone seen this happen before?