Comment by PhilMH:
Both Sides Now also has 1963 as the release year for the stereo version, and states that the tracks had extra instrumentation to make them stereo.
Comment by PhilMH:
Cash Box dated 25th February 1961 reviews this album, but only gives the mono catalogue number. Stereo editions listed in Discogs have master numbers starting with 63, and looking at MGM singles in 45cat, the last two digits of the mastering year seem to be the start of each master number, so I would say that the stereo version was mastered in 1963, and so most probably released that year (only one of the mono editions in Discogs appears to list the master numbers, which start with 60, suggesting that the album was mastered late that year).
Comment by whitewhale1965:
The linked albums have 1961 as the year of release vs this page. It would seem logical this item would be from the same year.