By late 1961 (or possibly early 1962) a sunburst color option was added, and in at least one Fender publication it was referred to as “Shaded Sunburst”.
In the course of 1963 the spacing of the two position dots at the 12th fret became narrower.
The profile of the neck gradually became fuller and more rounded, most noticeably towards the end of 1963. The Fender label on the headstock gained a patent number (PAT 2,573,254) in the middle of 1961.
In particular is a widely distributed photograph of an (implied) original sunburst Musicmaster that has appeared in many of the popular GPI books. In the case of any alleged custom color Fender, believe ONLY what you can see and verify with your own eyes.
The second version of the 3/4 scale Fenders are distinguished, like all Fender guitars of that period, by the transition from maple necks to rosewood fretboards; by the introduction of new colors, and by terrific quality control and attention to detail.
They next released the Precision Bass, and followed that up with the Stratocaster.
While all this was going on, Fender refined and added to their amplifier and steel guitar line as well.
The solid steel saddles were replaced with the threaded style saddles.
The anodization became a bit thicker and somewhat more durable on the pickguard.
By all accounts the research and development of Fender’s 3/4 size guitars (the one pickup Musicmaster and the two pickup Duo-Sonic) went very quickly.