I have just discovered (as part of the Leigh family archive that I bought from Cavendish) a partial example of the later "Crewkerne / Penny Post" unframed cancel (35x15 mm, SO 415) that according to the British County Catalogue (published in 1990) is previously only known in the GPO archive. Obviously this is subject to ratification (and there may have been other examples discovered since the BCC was published that I am not aware of). I plan to take the item to the March 24th meeting of the S&DPHG to see what they think.
The entire itself is fairly complicated, being from Brighton to Beaminster in Dorset redirected to Beggearne Huish (a parish of Watchet), and I'm not one hundred percent sure which handstamps were applied on which parts of its journey. Obviously the "BRIGHTON" single arc dated handstamp was on the first leg and perhaps the "BEAMINSTER" double-arc handstamp was used as a receiving mark. The framed "No.1" and "Crewkerne / Penny Post" handstamps should be on the second leg to Beggearne Huish.