I have a 1966 edition which, on page 21, shows a picture of a square butt OP and states, under STOCKS: "Full-checkered walnut, square built (sic). Can be supplied with round butt also."
The 1963 edition shows only that two page "Great Guns" ad showing all the current production, while the 1969 ad is identical with the '66 ad--even to the misspelling of "butt." I'd send a picture if I knew how. Gotta' get on that.
Both the 1965 and 1966 Gun Digest have this additional information, "Also available in round butt 4" bbl. 38 Spec." The 1963 edition makes no mention. Those are the only copies I have from the '60's.