Launched in 1989 alongwith the CDP-R1a and DAS-R1a , doing away with Philips' TDA1541A S1 ICs of the DAS-R1 and replacing everything with in-house Sony : 1-Bit PULSE d/a converters, SENS noise-shaping and 45-bit digital filters.
As in the CDP-R1a, the mechanism was revised to seal the spinning CD and have the tray itself be even more immune to vibrations : enter more "G" (Gibraltar) material, exit the BU-1 aluminium base.
As you can see below, the CDP-R3 isn't an R1a with an added d/a section as the drive and power supply remain different but the transformer is the same resin-potted Twin Core.
Unlike the R1a combo, the R3 integrated was meant to be sold only in Japan, even if a couple of units with native 120V (USA) and 220V (EU) found their way outside their homeland, probably as one-time Sony demos. The total production run was set at 2500 units.
Although used in quite a few contemporary players (Sony's, Denon's and Teac's - and others), the KSS-151A laser is nowadays, previsibly, not available anymore. And no laser = no player.
Extensively detailed views and descriptions can be found here - read them all and thoroughly !