What is this chrome 49cc engine? ..scrap yard find!

So this engine my brother found me at the scrap yard is not quite the same as the china girls ive been tuning over the years.This engine has a billet cover over the chain sprocket.The cylinder was slightly ported it seems and in kind of a v taper u can see in pics.The timing in degrees duration is .EX-140°,TR-110°, IN-120° Duration...slightly advanced intake it seems and the cylinder from bottom mating surface to top is 70.56mm tall where another china motor was 69.42mm tall with stock 110°Duration intake.It also has a much wider transfer area from the lower casing to match the cylinder no grinding required.So i just wonder where does this engine come from and is the crank possibly been balnced...it has a Z-L connecting rod.And i noticed its a solid crank with the two balance holes at top but two more farther down closer to center a lot smaller never seen this before. And these engine stamps all over u will see in pick same as on a china head i had gotten elsewhere.

Sorry you're right not billet but maybe chrome plated steel? Just a heavy solid chrome part unlike the rest of the plates covers.And what about the balancing.. i have not seen a crank with these extra holes in it before... there like maybe 1/4 " diameter and down in kind of a mid positon cannot tell if there weights in it or just holes as i have not split the motor.You can barely see these holes in the last pic... any ideas? And I am just trying to track down where it came from to see what the seller claims it has done to it or what if any performance mods it claims.