When I was in Brum last Thursday I used two or three thumb-latches. It was in the 'British Oak' pub, corner of Gooch Street and Wrentham St. I would guess it was rebuilt in the 1820s, when it was quite common to use a thumb latch rather than a knob you turned, or a lever handle you pressed down. By my time in the 1930s they were almost extinct, only used on front garden gates, but you had to have a front garden first.
Peter