Mitch A. Cotter used a FR-7f as his reference cartridge (but with silver body, silver Pins....). At that time it was also possible to order these carts with separate Diamonds, it was expensive anyway.
The FR-7 is available via ebay, normally no big deal to get one, same with FR-7f, but that one became rare in the last year, fz nearly impossible, the Japanese don't offer it outside Japan anymore...
Most have very low output (0.16mV-0.20mV), fz is highest with 0.25mV, you need a high gain amplification, in combination with one of their FR-Arms (64 for example) they easily compete with everything modern today.
In Germany are a few analog groups, some build their turntable with a piece of wood and a knife and think it is great, some prefer old Linn, Garrads, Thorens as the only, real solution to listen to and others refuse to listen to Linn, Garrads, EMT's for various reasons (BS, Waste of Time, wrong generally, colored) and when they have to, they want money for that...another group uses Seiki, Verdier from France, Cotter and that's it for them ....Another group in this little country have the motto for their reproduction stuff "You will eat your heart out", they are arrogant, don't read Mags or communicate in Forums because they are all afraid of getting eye cancer from reading that nonsense, hate reissues and their owners and accept only 2 colors: black or white ... :-)
And there is another interesting Country: France
From there the real outstanding Japanese stuff was translated in the early 80's, introduced, built and there are also some very interesting audio circles ....
The carts from Fidelity Research were made until 1989. From what I know, the FR-7 series are different among with Impedance, Output and what kind of diamond cut they have. They last forever based on their internal construction and can be retipped quite easily. Extremely high tracking ability. One or two of them are a bit special, they were made for Japanese Press Plants to listen with them their Test Pressings, there was also a FR-1 / FR-702 available....