With the help of Vic Rosewarne the flask can be dated to between 1827 and 1850. The Kensington Division Licensing Records for 1827 has a list of transfers including:
     At a Special Meeting of the Kensington Licensing Magistrates on the 3 of November 1827 - The Barge Aground was transferred to Thomas Perress from Hannah Marnham.
Robert Perress is listed as the licensee of the Barge Aground at the 1828 Licensing sessions; the licence was transferred from William Perress to William Barker in 1850 (see Vic's list of pub transfers for more details).

The Barge Aground was at 361 (later 362) High Street, a few doors west of St George's Church; type "Barge Aground" in the search facility to find other references on this site, a couple of photos showing the pub in the 20th century and also read about its ghost...

Neil's website London Saltglaze Spirit Flasks has more information and several images. Look for the 1820's flask produced at Mortlake for Tayler at the Hand & Flower, Old Brentford (tab marked 'Potteries').

If you have any more information relating to the Perress family, or the Barge Aground, Neil would be very pleased to hear from you. He can be contacted via the BHS website.