This water jug is very close to matching pattern 7043 in the Molineaux Webb pattern book - only the 4 leaf clover on the body and the twisty handle differentiate them. Pattern 7043 was made about 1865 give or take a year so is a good indication as to when the piece above was made. 7043 came in 4 varieties, one as a decanter with stopper, and 3 variants of unstoppered water jug, one very squat with a matching goblet, one less squat and a longer one which didn't have a round top - more of a tip & pour teapot top (grrr - what's the word for this, brain addled today).
The pattern varied a little on 3 of the pieces, and substantially on the other, using a Greek Key around the body but still categorised under 7043 pattern number.
It is indeed very difficult to match these to a maker. After 5 or so years with the M&W pattern book I have hardly found an exact match for anything, and suspect many cut pieces were one offs, even if they made it into the book.