Upgraded limited edition of the 1000ZXL master recorder, in fact so limited it was built on order only - outside Japan that is.
The upgrades consist of gold-plating treatments (front, chassis, flywheels, heads shielding, terminals), corrosion and vibration care (sandwiched aluminium with black alumite for the transport, black chromate for the chassis), solid brass (flywheels), hand-picked parts (PCBs), copper added (ps heatsinks) and a rosewood enclosure.
Plus an engraved personal nameplate placed under the cassette window ; the one you see here was Niro Nakamichi's own unit. Many decks, however, have the plate but no name engraving...
Official specs are marginally better than the normal 1000ZXL but the measured specs do exceed those published for each deck made, as found out by Audio (US) in september 1982.
Even if not to a night vs. day, extent the overall response and s/n ratio are bettered, and distortion sligtly reduced ; channel separation and erasure ratio are however significantly boosted.
The total production run is unknown but like everything gold it sold well despite thickly plated pricetags : 6000$ in the US and 850,000¥ in Japan - a 300k¥ supplement !