There are several CDPs that use that laser.
Denon DCD - 1000, 1500
NAK OMS-3 and 30
Onkyo C-700 Integra
Sony CDP 40,45,55,65
I am pretty sure KSS parts are from Sony. I don't know for fact but from experience and from what other people say.
Several years ago I bought some KSS-151A and the outer box says Sony for SURE.
I hope you didn't pay $100+ for this part because the CDP that use this laser don't seem to be high end.
wsjoe
Guiller
which is your favorite cd player?
This mechanism from Kyocera DA-....CX players or from its clones (by ADC or DBX or VECTOR RESEARCH)
Sometimes in this mechanism was KSS-152A
Although this list is not exhaustive, there are several CDPs listed there featuring kss-121a:
ADS CD3
BRAUN CD3
DENON DCD-1000
DENON DCD-1100
DENON DCD-1500 ( I had this one, it' s a great CDP!!!)
NAKAMICHI OMS-3
NAKAMICHI OMS-30
NESCO HCD-50
ONKYO C-700 Integra
SONY CDP-40
SONY CDP-45
SONY CDP-55
SONY CDP-65
All the best

Guiller - many thanks for this list. It's larger than the one I was able to cobble together.