Not much is known about the history of the 2x series. Depending on how you see the 19s relationship with Standard Radio of Japan, the 2x series is either the 1st or 2nd. The 19 initially was assembled in the US anx then latter the 19 was kitted in the US, sent to Standard Radio where it was assembled, and then sent back to the US for final quality control testing and packaging. All components down to the last bolt and nut was the same as the US assembled unit. Some assert the 19 is the 1st Japanese, others like myself do not as all the engineering, significant parts, final testing and packaging was done Stateside. The label on these state they were "assembled" in Japan, not manufactured.
The 2X series were a hybrid Standard Radio and Marantz component. For the most part the innards are stock Standard Radio, the regular tuning knob Marantz had replaced wkth the Model 19 thumbwheel, their exclusive signature except for when JVC stole it For a couple of series and ended up in court. Not sure about Citation's thumbwheel. Marantz at that time was in financial straights and may have sold a license for its use to HK or the patent had run out. The 19 faceplate became the company's flag bearer with the thumbwheel. The 2x series used an engraved version of the 19's design. Also the knob design was lifted from the Marantz line. All in all they sort of looked like a 19. More importantly where Saul wanted the18 facia to be the new Marantz look, the brothers over road him and went with the 19 look in effect constructively removing him as the company President and as an employee. He walked and a day later the entire engineering group also left. This was a total radical clean sweep of the company's engineering. Going forward the new team had nothing from the past. The 22xx series was still a Standard Radio design but, the new look was taller, closer to the dimensions other companies were promoting successfully while under the hood the circuits were carried forward from the 2x series. In the case of the 2270, this carry forward was a might too much with the tone amp. The working voltages were increased but the components specs stayed the same and the dream machine died almost immediately after being plugged in.
I hope this answers your question.