Are they Zeiss Contax? If so they should be pretty good lenses. The Zeiss Contax lenses have some incredible lenses in the set. I just switched over to a Contax kit. I cant speak for the 50mm 2.8 and the 135mm but some of them are truly fantastic. The 35-70 3.5 is said by many to be one of the sharpest zooms in slr lenses. They say it competes with many primes and beats some as well. I just ordered one and am stoked to see if its true.
Check out this well made article for more info on Contax glass.
http://www.reduser.net/forum/showthread.php?92044-Contax-Zeiss-Survival-Guide