Sony's first foray into HIGH-Fidelity, before the FET, V-FET, High fT and MOS-FET revolutions... and before all other manufacturers.
The TA-1120 and later TA-1120A are basically the same amplifiers with mainly parts changes in the preamp section.
Visually almost identical : the headphones' front terminal was replaced by a "safety" LED on the 1120.
Inside is very close to a TA-2000 (or vice-versa) : solid steel chassis, function stages just behind the front plate, filter / flat amp / EQ boards next in the shielding case, protection (x1) and DC bias / AC balance (x2 each) vertically in the center and power stages at the back.
Like the TA-5650 or TA-E7B, the back-plate pivots to allow easy access ; preamp stages are ps-regulated ; idle current is to be set at 50mA.
Old days detail : left and right NAB tape eq adjustments pots are located on the underside.
Both versions were highly praised, sold extremely well and were meant to be used with the TA-4300 channel divider and the various power amps Sony had then available which were all very successful, too :-)
The TA-1120 was the very first ES component, in 1965 - that's right : ES is as old as 1965.
And ES stands for Extremely High Standard. Just as successful were the supremely elegant TTS-3000, ST-5000, PUA-286 and PUA-237 tonearms.
Looks-wise, it should be noted that the Sony logo, encased in the upper horizontal recess, one of Sony's early design trademarks, is a trick re-used for quite a few units throughout the late 80s (TA-F830ES etc).
And if you check an SCD-X9000ES or the recent ES receivers, you'll find the same signature, although in a much less discrete manner.
Superceded by the TA-1120F which remained available in Japan as late as 1976 given the japanese standards it was quite a feat. And pricier than a TA-5650 V-FET, mind you !