Casting numbers, sort of?

Alrighty, here's the deal. Quite some time ago I bought a rod/piston combo for pretty cheap because I was planning on re-building a 6-bolt and doing weird things with my RS, that thought is now far out the window. But when I bought them, I remember the seller saying something about the pistons are a special piston, but I can't for the life of me remember what he said he thought they were from. I haven't hardly looked at them for the past year or so, but they're just laying around and I want to get rid of them. I had my dad take some numbers off them and I was hoping that some of you more experienced guys might have come across a set like this before. Anywho, enough with the story. The numbers are as follows:

On the top the piston there's a number that reads 63DT.
On the skirt/wrist pin side (I believe that's what he told me): ART5L
The rod has a G6P with an N on the cap.

I'm almost 99.9% sure that they're 1g "big" rods, but can't remember about the pistons. Anyone have any insight about this crap? Gracias.

I can check when I get back to my room, but I am pretty sure those markings on the top of the piston were the same ones I have on the tops of mine...