All Nak BX,CR,DR,CD and the RX202 decks use sankyo. All older nak decks use nak transport. ZX7,ZX9,LX5,LX3,Dragon,480,481,680 series,RX 505,RX 303 etc etc etc.
There are four transport mechanism families related to Nakamichi.
The first is the original single-motor dual-capstan of the 1000 and 700. Then there is the single-motor single-capstan transport of the 600, 500, 550, etc. and likely the decks Nakamichi OEMd before they started under their own name.
But all these are regarded antique and are seldom the subject of discussion these days.
That leaves two families: the Classic transports (48*, 58*, 68*, 1000ZXL, 700ZX*, ZX7/9, Dragon, RX) and the Sankyos (see above).
The Classic transport was almost certainly designed by Nakamichi, but I am not 100% sure they actually built it. AFAIK there was a major agreement with Sankyo(*) over a long time. Who builds what in Japan is mostly moot anyway, as they have/had a tradition of deeply-nested subcontracting, with small, unknown companies often doing most of the work.
The generic transport known as 'Sankyo' emerged with the Onkyo TA-2055 in 1982 (single-capstan direct-drive). Already in 1981 the TA-2060 had a very very similar mechanism, but actuated by solenoids instead of a cam motor. Later in 1982 Nakamichi for the first time used a Sankyo, in the BX-1 (single-capstan belt-drive). Given that Onkyo seems to have been the first customer of this transport, it is unlikely that the family had been designed with of for Nakamichi, although there must have been some customisation through the years. But that holds for every customer. It is also not certain if Sankyo built these mechanisms. Most likely it got its name during the recent cassette revival, because many of its instances proudly have 'Sankyo' on the reel motor. (Sankyo also was the supplier of the entire direct-drive motor system, right up to the final quartz-locked version used by TEAC). So, who made the Sankyos? Might be Sankyo. Also might be Alps: the large dual-capstan transports of the big Luxmans, Alpines, and Alpages also have a lot in common with the Sankyo drive!
There are some nuggets of information in the Nakamichi book (
https://www.cdjapan.co.jp/product/NEOBK-2456125), but (machine) translation is hard and bound to confuse matters even more. I really should find the time to approach one or two people capable of a decent translation ... And even then the book, written only a couple of years ago, may well be wrong in this matter.
Once past the OEM times Nak really never supplied any other manufacturer with their unique crystalloy heads. In doing so they would have given away their single-most important performance advantage. But I do happen to know of a hobbyist who transplanted Nak heads into a Yamaha KX-1200 or whatever. Both decks being Sankyo-based that was not too arduous.
(* Confusing, not?)