Next to none. The ones that exist may all have been salesman samples--perhaps a dozen or fewer.
Remember that commercial distribution of the K-32 didn't really get under way until February of 1949, nearly a year after the four-line order came down from on high. At least two K+four digit K-32s are known, and both apparently have large ejector rod knobs. These guns were produced in 1946, according to factory records. There is one known commercially distributed LERK K-32 known from 1949. It is possible that the K-32 Masterpiece is the only masterpiece model in which the vanishingly rare LERK specimens outnumber the even more rarely encountered single-line variety. But with only three specimens to talk about, it is hard to be sure.
David - I sent Roy a letter request last week on my K-32, single line, LERK seen in the link below. Based upon recent letter turn-around times it will probably be a while before/if we know any more about this one. Mine is a March 1948 gun.
http://smith-wessonforum.com/s-w-hand-ejectors-1896-1961/363443-k-32-serial-number-k2244-new-info-post-11-now-new-pictures.html