Antique Pewter has dated this piece to the 1880s.
There are also ownership initials 'IP' stamped on the lid. There are also the 'five-leafed rose' and 'fleur-de-lys' Guernsey verification seals stamped below the rim.

The flagon is in excellent condition with a polished silver-grey finish, note that the inside is coated with possibly paint from the flagon being used to hold artists brushes or similar. (This is reflected in the price).
Circa 1800.
Size:
Height: 8.50 in (21.50cm).
Base diameter: 4.125in (10.00cm).
Shipping costs:
UK: £12.00
Europe: £30.00
USA/Canada: £40.00
Other countries: Please ask.
Stock number: P-061.
Antique Pewter has dated this piece to the 1880s.
Antique british & european pewter.
You can view the stock and full dealer information on the Antique Pewter Profile Page