Gibson's "Mastertone" line of higher-end banjos debuted in 1925 with style 4 as its next-to-lowest-priced model. Style 4's original specifications included straight-grained mahogany with a brown stain; there were two narrow concentric rings of white-black-white purfling on the back of the resonator and the neck, resonator, and heel cap were bound with multi-ply white and black binding:
The hardware was nickel-plated (with the exception of a few chrome-plated examples) and, as with other early Mastertone models, included a two-piece "tube-and-plate" flange and a grooved tension hoop with flat hooks:
In 1925 and 1926, all Mastertone models including style 4 featured a ball-bearing tone ring with sixty holes:
The earliest version of this ball-bearing tone ring, seen primarily on examples from 1925, also had holes in the outer skirt:
Style 4 Mastertone banjos from 1925 to 1928 featured a fiddle-shaped peghead and the "hearts and flowers" inlay pattern in a rosewood fingerboard:
The earliest version, seen primarily on examples from 1925, had the word "Mastertone" inlaid in small individual letters on the peghead just under the script "Gibson" logo:
Circa 1926, the word "Mastertone" moved to a mother-of-pearl block at the end of the fingerboard:
Circa 1927, all Mastertone models including style 4 changed from the ball-bearing tone ring to a cast metal raised-head, or archtop, tone ring. While the exterior "beveled" appearance of the head remained the same, the new tone ring construction is evident inside the body, with some of the earlier raised-head rings having no holes. . .
. . . while the forty-hole variety soon became the standard on all Mastertone models:
With the change to cast raised-head tone rings also came a change to notched, rather than grooved, tension hoops with round, rather than flat, hooks:
Style 4 Mastertones of the 1920s were typically equipped with the Grover Patent Presto tailpiece:
In 1929, Gibson redesigned its Mastertone line. For the style 4, this meant a change from the two-piece "tube-and-plate" flange to a one-piece flange made of die-cast "pot metal":
The plating changed from nickel to chrome:
The neck and resonator were changed from mahogany to walnut, with two concentric rings of multicolored wood purfling on the back of the resonator:
The peghead shape changed to the "double-cut" design and the standard inlay pattern was changed to the "flying eagle" design:
Although some examples continued to be made with the older "hearts and flowers" design:
The forty-hole raised-head tone ring remained standard on style 4 tenor banjos in the 1930s, but style 4 plectrum and five-string banjos were now routinely fitted with the new flathead tone ring which, according to Gibson literature of the time, imparted "greater brilliancy, sweeter tone, more volume and easier respone" to plectrum Mastertones and "extra twang and ring" to "regular", or five-string, models. The flathead tone ring allowed the entire surface area of the head to vibrate freely. Inside the banjo, its sloping inner face is clearly visible; some early examples were made with no holes, but the factory soon settled on a twenty-hole design:
Style 4 banjos featured the guarantee label found inside the rim of all Mastertone models (see above) as well as a factory order number stamped inside the rim. . .
. . . and written inside the resonator:
By 1937, declining banjo sales prompted Gibson to drastically overhaul its banjo line; three new top-tension Mastertone models were introduced and all existing Mastertone models from style 4 up were discontinued. Style 4 would remain out of production until being revived by Gibson in the early 1990s.