This is a very rare high-end amp, with only a handful ever made. The Cavalli Audio Stacker II hybrid amp, the predecessor to the Liquid Glass.
The amp was specially designed and built to drive orthodynamic headphones, but works with many other headphones as well.
Some of its features includes.
a brand new broskie high voltage power supply at 275Volts
fresh build and brand new case
green LED light around the power button
AmpOhm 0.22uF Aluminum foil PIO coupling caps
Toshiba 2SC2238/2SA968 output devices in the buffer
TKD 2CP-2511 potentiometer
Vampire RCA jacks with loop out.
Schaffner filtered AC inlet
Can run 6.3 volt novals (6CG7, 6GU7, 5814) OR Octals (6SN7) tubes in the input stage