Ray:
CS stands for "China Shanghai". I toured the Shanghai Model Engine Research Department as a guest in 1994.
(It's located in the area of the City of Shanghai & district, of course)
Home Tuned/modified versions of CS .049's often win/place at the U.S Nats in 1/2A Profile Proto & 1/2A speed.
A good comparison of .049's can be found on the web site of Martin Gregorie.