Our fellow member Fotohuis once did a bit of testing on this film. And though being a Maco dealer he put some critique on Maco statements on this film. He considered R3 and D-76 a non-fitting combination.
Maco meanwhile stated that they no longer will have the R3 manufactured. Then short ago they reported to seek a solution for customers longing for that film.
Anyway the R3 was designed by Filmotec and is basically their TC27 coated on different bases. The TC27 however is only available as 35mmDP.