When you ask "what edition" I assume you mean "what issue" and this is only a term used in the Blue Book Values and a lot of the old timers have a problem with "issue" because the BBV's is incorrect. But to answer your question, it's a 5th issue. One can tell that buy looking at the mfg date mentioned. Hope this helps.
bcs1487: You got yourself a fine Colt 22 revolver. What kind of shape is it in? The Officers Model Match (OMM) was THE Colt target revolver, especially in 22RF. The "Fourth Issue" is the Officers Model Special which was produced for only a short period between 1949-1952. The OMM was introducted in 1953 and discontinued in 1969. At the time the OMM was discontinued, Colt had just introduced the 22 version of the Diamondback revolver in 1968 which was also considered a target grade gun, although some disagree relative to the accuracy.