When working on my bike today i noticed a stamp on the side. Very small it reads RMR in a diagonal pattern. Anyone have any idea what thats from?

Oh dang, Maybe was a little bit to tipsy when I posted that. 
That should probably read Cylinder instead of head. That is where the stamp is, I would of posted a picture but my cell currently refuses to work properly. The stamping does not appear to be an OEM marking. The cylinder seemed stock to me but I'm not entirely sure.