Although there were plenty of market-related versions of this generation of decks, the TC-229SD seems to be a really rare one and probably an export-only item.
Inheriting the supreme feather-touch transport design of the ELCASET decks (and even the RM-30 remote control), this was no masterpiece (neither was it meant to be) but a huge and very sturdy deck from the mid 1970s, set into the chassis of an EL-4 / EL-5.
Two F&F heads, one DC Servo motor for the drive and one AC motor for spooling, switchable MPX filter, a switchable limiter, FeCr compatibility and even a Rec-Mute switch.
Later on upgraded as TC-K7 (II, B, BII etc) and TC-K8B - serious, no frills, indestructible.