What are this # on the piston

[Slowy-gonzalez]

I bought a couple of 57 trucks one does not run, it was left under a tree for years without the hood and for sometime without the dist., it had a double carb set up and all that rain water going down thru there, this truck has operating air bag system, with a notch on the frame, along with good alum radiator, chrome pulleys, etc etc with that in mind, and because the other truck engine has good amount of $ into it, I believe the truck that is not running might have good brand or quality internals, took the head off and its bad , now I am just wondering what the numbers 05-347-07-c on top of the piston might mean.