Sleeper alert!
October 15 2014

Picture: Tooveys
The above picture came up at an auction house in West Sussex the other day, catalogued as '19th Century Continental School, and estimated at £70-£100. It made £406,400. So, a nice surprise for the vendor.
More images here. Looks like a Greuze to me.
Update - a sleuthing reader writes:
The Greuze sketch was probably the one given by Greuze to the engraver Johann-Georg Willie on Nov 27th 1759. Willie describes it in his journal:
M. Greuze, this serious, solid painter, has just made me a present of one of his excellent drawings, a sign of true friendship. The drawing represents a kitchen maid stainding next to a cupboard, reading or calculating in her account book, after coming back from market, how she can best cheat her mistress. It is of great beauty, and boldly drawn.