I'd say that one is near the end of their run -- 1835-1840ish. I also just checked my Tweedale directory, and he records that the Brittain and Brownell families parted ways in the late 1830's and that the Brittain family continued producing edge tools under their own name (though the biz was being run by George's son, Verdon).
As for the anchor mark, all there are are guesses and until some period sources turn up, I don't place stock in any of them.
The mark is ancient. Here's an anchor stamped razor from the 15th-16th century, probably made in Germany.
https://uploads.tapatalk-cdn.com/201...a953f8625b.jpg