Butter Fingers at The Old Dairy, Crouch Hill

Last week I was chatting to Jason at the Oxfam Books & Music shop at Crouch End as I assessed my card stock there. As I added some more of the Old Dairy at Stroud Green he asked if had noticed that one person depicted on the sgraffito panels had something extra.
Intrigued, I walked back down the hill to take another look.

Cards

I have studied these panels many times but although I had noticed that the people aren't what you'd call beautiful and are mostly out of proportion with the other characters and objects around them, I hadn't spotted that one of the butter-making girls has an extra finger.