Teisco was a Japanese manufacturer of affordable (cheap) musical instruments from 1948 until 1969. They were imported into the US sometime around 1950 and were often rebranded by other "affordable" guitar companies. Teisco typically copied the popular guitar designs, but the T-60 was an original design that had a "monkey" grip in the body, and the cutout in the headstock.
The T-60 was entirely handmade and very ambitious for its time. It features a fine set-neck design with a deep-V neck profile and solid-wood construction. The pickups, designed and produced in-house, feature adjustable pole pieces. They measure in the mellow 4kHz range, but sound quite lively The rotary switch permits individual pickup selection, and each pickup offers nice, round tones with a touch of twang—somewhere between a Stratocaster and a Telecaster. Probably the most striking feature of the T-60 is the “monkey-grip” body cutout and the headstock that echoes it. This was the first instance of this signature Teisco feature, and on the T-60 it was carved completely by hand. T-60s were produced until 1961, but then disappeared, when Teisco started mass production for N. America.
Here is a page from the Teisco Japanese catalog showing the T-60:
I am not sure why Glen took a liking to this guitar. You wonder how he found it (it wasn't an export guitar)! It certainly was inferior to the Fenders and Gibsons, but he showcased it in the early 60's on Star Route
as well as other shows.
Additionally, as witnessed by this picture
, Glen used the Teisco while with the Wrecking Crew, as well as HERE
Glen soon moved on to using a Fender electric, Mosrite, Ovation, back to Fender, then to G&L...but it is apparent that Glen had fond feelings for his T-60 because it was one of the guitars he choose to surround him in this picture that was taken on his staircase in Malibu: