Poster for a 1939 stage production.
The title stands for Rossum's Universal Robots, although in this case "robot" refers not to mechanical men but to artificially grown people. Drawing on the Jewish folktale of the Golem, it is an overtly political play in which the enslaved robots stage a worker's revolt against their human overlords. Sci-Fi-London is planning to do a new adaptation of the play and they've posted a reading online which provides some idea of what that historic TV broadcast might have been like.
R.U.R - SFL reading