One of the few Sansui open-reel recorders, available in two versions :
5500 : strict 4-channel,
5500S : with 2-channel playback compatibility.
Both were built not by Sansui but either around a Teac mechanical base (c. A-6010GSL, 1972, at a time Teac was also feeding drives for Denon, Sanyo and Diatone) or... Pioneer as the capstan/roller/lifters/guides and mostly the motors look very reminiscent from the RT-2022 series. And the same motors were used in the RT-909, too...
Whatever, whoever -
the audio part was however naturally entirely Sansui and the hard permalloy heads seem to be as well (but I doubt it :).