Quick question.
Are the models in Japan naturally called t30/40/50rp mk3n with the "n" at the end? Or are these a newer revision?
http://www.fostex.jp/products/t50rpmk3n/
http://www.fostex.jp/headphone-earphone/
I compared the technical specs with the non 'n' version and they are exactly the same so I wonder what may be the differences, if any.
It is a little historical, and a little confusing. I think it's retained from the days of the MK2.
When the T50RP came out, it was the "MK2" family with the 35mm square driver that we all love today. However, during that era, there was the T20v2 and T40v2 (note v, not Mk). Those had 45mm circular drivers, which were jammed in between two large magnets, and the whole baffle was essentially a single piece.
The T20MK2 and then T40MK2 were released, pretty much T20v3 and T40v3. This is when the T50RP returned. We call it the MK2, however it was just marketed as a "T50RP" considering the last T50 looked like the super-vintage T50 "Mickey Mouse" looking T50's.
The original release of this T50RP had some nasty pads, and essentially downplayed the greatness of the 35mm square driver--it was thought to lack bass, completely. A minor revision happened, which is only represented as T50RP Mk2n by say, 2008-ish, and the pads were revised, and I'd say this is when the headphones started to really gain their fame in being the modder's dream Planar headphones.
These days, everything has been normalized as "T*0RP MK3." I noted that Amazon.co.jp still retained the "n" moniker for some reason, but they're the same.