Auctioneer Andrew Potter noted the marks for Brownfield but could find nothing similar from the Cobridge, Staffordshire, works.
Eight years ago, a couple of Brownfield teapots sold well: one formed as a Chinese man wrapped round the pot took a 20-times estimate £1950 at Fieldings, Stourbridge, and one of Brownfield’s prize fish teapots made £2250 at Christie’s South Kensington.
These were outlier bids in a falling market, and today Brownfield majolica usually commands two-figure or low three-figure bids.
Potter guided the 8in (20cm) long teapot with the lid formed as a Japanese man’s head at £150-200 for the auction on August 11.
Online collectors took bidding up to £700 at which point a room bidder stepped in – Kent collector Paul Roberts, who has been collecting teapots for 30 years and now owns more than 6000.
Having seen off the online rival with a bid of £850, Roberts said: “I can date the teapot to 1876 but I’ve looked in all my books and can’t find it described, it’s so rare.”