FWIW, there are two DV sites: Japan and the US distributor. US link here: http://www.dynavector-usa.com/dynavector_dynavector.html. The 17D3, TKR and others are all still available from the US operation although some may be NOS. I've found them very helpful and responsive over the years. Mike Pranko there might be a good source for background on some of the finer points of DV history.
As I recall, the Karat 23 was the first iteration and always had a ruby cantilever and silver body, followed by 23R, 23RS and finally MR 23RS (I think that's how the nomenclature on the label went). The MR was the micro ridge edition. The Karat 17 was presented in a gold tone body with the diamond cantilever. I believe it went 17, 17D, 17D2 to the present 17D3. I loved my 23s and was disappointed I couldn't readily achieve the results I expected with the 17. I was very enamored of the short gemstone cantilever design.
That said, things change and the XX2 I have now is definitely a superior product to the 23 or 17.
As I recall, the Karat 23 was the first iteration and always had a ruby cantilever and silver body, followed by 23R, 23RS and finally MR 23RS (I think that's how the nomenclature on the label went). The MR was the micro ridge edition. The Karat 17 was presented in a gold tone body with the diamond cantilever. I believe it went 17, 17D, 17D2 to the present 17D3. I loved my 23s and was disappointed I couldn't readily achieve the results I expected with the 17. I was very enamored of the short gemstone cantilever design.
That said, things change and the XX2 I have now is definitely a superior product to the 23 or 17.