0ZeR0: There is much of interest said about this endgame in the book Frank Marshall, United States Chess Champion: a Biography with 220 Games by Andy Soltis:
"Almost nothing was known about this exception to the general rule that two extra pawns generally win. (A previous example Albin - Weiss, Vienna 1890, drew little attention) With a rook pawn and a bishop pawn the winning task is much more difficult since the defender's king can block both pawns, as Marshall continued to do here with 58.Kb2.
Rubinstein saw that a pass move such as 58...Rb8 would allow 59.Rh4+ c4 60.Rh7! and black cannot make progress. So, he played the natural 58...a3+? 59.Ka2 Ka4, shielding his king (60.Rh4+ Rb4).
But Marshall found an active but effective policy: 60.Rc1! Ra5 61.Rb1!! after which black was stopped. The Pole tried 61...c4 62.Rb8 Rc5 63.Ra8+ Kb4 64.Rxa3 and conceded the draw after 64...c3 65.Rb3+ Kc4 66.Rb8!.
The subsequent analysis - seeking to find the forced win that virtually all fellow masters felt must be there - led to the discovery of an intricate variation that begins (after 58.Kb2) with 58...Ka5+!. Then on 59.Ka2 black can push the c-pawn: 59...c4 60.Rh8 c3 61.Rc8 Kb4 and 62...Rc5, or 61.Ka3 Rc5 62.Rh1 Kb5 63.Rg1 Rd5! 64.Rh1 Kc4 65.Rg1 Rd2 66.Rh1 c2 67.Kb2 a3+ 68.Kc1 Rd1+ 69.Rxd1 cxd1(Q)+ 70.Kxd1 a2 and wins.
On the other hand, if 59.Kc3, then black wins with 59...a3! 60.Rh8 Ka4 61.Ra8+ Ra5 or 61.Rh4+ Rb4 62.Rh8 Rb3+! 63.Kc2 Rb5 64.Ra8+ Kb4! 65.Rh8 c4 66.Rg8 Ra5 etc.
The family of rook, BP and RP positions is so notoriously complex that Mikhail Botvinnik, born the year this game was played, decided that he must master it before the 1948 world championship tournament because he didn't deserve to be world champion if he didn't understand it."