"Robert Browning." Victorian slang for?

[Vanessa]

What does Robert mean in the scene where Nan meets a man outside the tobacco shop and he asks for a Robert? "A sovereign for a suck or for a Robert'- he meant of course, a Robert Browning 'Half a guinea for a dubbing.' "

I'm guessing Robert Browning, or browning the robert, means anal sex? And dubbing means a hand job? Do those terms really exist or did Sarah Waters make them up?