it looks like the fr24 was a mid-late 60's design, the bearing design looks really interesting. I cant find any reviews on it, much like the fr54 the 24 was a japan only model so info is going to be hard to come by. Not very many people are hip to Fidelity Research, I dont think I have seen anyone else with an fr54 on this forum, come to think of it I dont remember seeing any FR tonearms around here. I am sure some other guys have to have them but they are not common by any means.
Like I said, info on Fidelity Research is scarce and confusing, I had an ex-FR dealer argue with me that the fr-54 never existed and I had to be mistaken about the model number, but one thing everyone seems to agree upon is that FR are great sounding arms with second to none build quality.
good luck with the arm, please let us know what you think about it if you get it.