By the end of 1936 Gibson unveiled its first production models of electric hawaiian and spanish guitars in catalog "X" , the EH-150, EH-100 and ES-150. These were accompanied by two new amplifiers. Guitar and matching amplifier were offered as a complete outfit including guitar case and cords but could be purchased separately. Model designation reflected the price for the package offer. But this was preceded by a year with an aluminum bodied lap steel, known as the E-150, and a 4-tube amp (picture above) that was the fruit of a collaboration between Alvino Ray, as musical advisor, John Kutilek, electronics engineer for Lyon & Heley, and Gibsons Walter Fuller.

The early production model EH-150 lap steel (below) received a wooden body. Tone and volume controls were fitted at each side of the new "Charlie Christian" pick-up.

Later, these controls would be located on the same side of the lower bout of the body. The instrument would also receive a fancy headstock inlay.

The EH-150 amp cabinet was covered in "Aeroplane cloth", luggage tweed, with contrasting vertical brown stripes. A black perforated aluminium grille protects the ten inch "Ultrasonic High Fidelity Reproducer" speaker. Later Gibson would often affix red stickers onto the back of speakers with the printed text "Ultrasonic Speaker". Especially during the '60s and '70s. Chassis were mounted at the bottom of cabinets. The features of the early EH-150 amp include one input for microphone and three inputs for instruments, separate volume controls for the microphone and instruments sections, a bass-tone expander switch, and an "Echo" extension speaker jack.

As mentioned, catalog "X" also introduced the EH-100 set. The maple bodied lap steel in black ebony finish with white binding features a single volume control. The spec for the finish was changed in 1937 into sunburst and a tone control was also added next to the volume control.
The early EH-100 amplifier cabinet was covered in black leatherette with the Gibson logo stenciled in white at the lower right front corner. A black perforated aluminium grill protects the ten inch speaker.
For the single input stage of this early EH-100 amp, one 6N7 (high-mu twin power triode) was used, along with two 42 (power pentode, a predecessor of the 6V6 I guess) output tubes, and one 80 rectifier tube (which had almost identical electrical characteristics to the 5Y3).
The EH-100 amp was then revised annually, circuitry-wise as well as cosmetically (see specifications).

The 1940 EH-100 amp cabinet has got a detachable bottom part containing the chassis. Both amp and lap steel (similar to the later EH-125) in natural mahogany finish. The EH-100 amp and lap steel was replaced in 1941 by the EH-125 set.

The EH-125 amp looks a bit like the late style EH-150 amp. Two 6SQ7 (high mu triode) was used for the early EH-125 amp input beside one 6J5 (medium mu triode) as phase splitter, two 6V6's for output, and one 5Y3 rectifier tube. This amp also uses a twelve inch field coil speaker for its output.

A natural maple finish EH-275 amplifier was introduced in 1940. Special order AC/DC versions of EH-150, EH-100 and EH-185 known as EH-160 (3-6C5, 4-26B6, 4-25Z5), EH-110 and EH-195 respectively were also offered as well as 6VDC, operating from car batteries, and 25 or 50 Hz, 220-240V versions. Gibson would also for the first time unleash its own budget brand "Kalamazoo" alongside the "Mastertone" trademark and offer a set of lap steel and amp, known as the KEH (see the beautiful sample below).

A two-piece cabinet Kalamazoo amp in a smooth brown leatherette covering was available in ca 1940. Both amp and lap steel are similar to the 1940 EH-100 set.

A medallion and a licence sticker found on the inside of the KEH amp above gives more clues as to who manufactured these pre-WWII amps for Gibson. "Licenced by Electrical Research Products Inc." and GEIB, a manufacturer Gibson subcontracted to make guitar cases. Such licence stickers and medallions are often found inside EH-150 and EH-100 amp cabinets as well.