He once bought a collection of 19th century watercolours, and some of these were hanging on the walls. The rest was off the peg, Smiley decided. Maston was off the peg too, for that matter. His suit was just too light for respectability; the string of his monocle cut across the invariable cream shirt. He wore a light wollen tie. A German would call him flott, thought Smiley; chic, that's what he is - a barmaid's dream of a real gentleman.
What does off the peg mean here? I understand that it means ready-made. Does it mean the same here when referring to Maston? Why would barmaids think of him as chic when his suits is ready-made and lacks respectability? And the sentence "the rest was off the peg" refers to the short piece of wood used for hanging things (i.e. the rest of the paintings were not shown)?
Source: Call for the dead (John Le Carre)