Production of the LES PAUL JUNIOR began in 1954 and ended in 1960. In 1954 Gibson Introduced its first all-mahogany flat-top solidbody guitar, the Les Paul Junior. The body of this instrument was shaped much like the backs of arch-top Les Paul models, with a single cutaway. The Junior was the first Gibson production solidbody to carry only one pickup. and it came in a sunburst finish. In limed mahogany it was known as the Les Paul TV, this finish apparently making the instrument stand out better on black and white television.
By mid 1958 the Junior had been redesigned with double cutaways. The new body was thicker with smoothly curved edges and well-rounded cutaways. The upper cutaway extended slightly beyond the lower, and the neck now joined the body at the 22nd fret. This version of the Les Paul Junior was available in cherry red or, again in light-coloured limed mahogany, as the Les Paul TV.
In March 1959 the new double cutaway body was adopted for the two-pick- up Les Paul Special, available by this name in both cherry and limed finishes. In 1960 the Les Paul TV of 1958 and the 1959 Les Paul Special were renamed SG TV and SG Special. The "SG" designation was applied by the Gibson sales and management department, the initials standing for solid guitar, and it seems likely that the decision to rename these instruments was not made until after May 1960. Finishes and specifications remained the same, but the gold "Les Paul" script was deleted from the headstocks. At least some of the SG Specials were built with necks and fingerboard pickups set slightly farther back in the body than the Les Paul Special of the preceding year; this modification was apparently intended to increase the rigidity of the neck to body joint.
References: Guitar History: Gibson SG By John Bulli