Hi - you might try the IrfanView re-sizing programme - free to download and very useful. Not sure of the size of your pix, but if you can get the first dimension to 700 that will help.
I've had a look at TNA pix for the four Sowerby Registrations you mention - three of which are vases and one a plate - none is a handled jug with lip, in the shape of the piece you show here, which indicates that the protection offered wasn't for the shape of your piece (that's assuming you have read the lozenge No. correctly). However, the three Sowerby jugs from that date all appear to have some some form of surface decoration in the form of plant forms, though whether any of the decoration on them matches the decoration on your piece I can't tell as your pix not clear enough to make an accurate comparison. In general, Registrations were either for the design/shape of a piece or alternatively for the decoration only, and it may be that the decoration on you jug does match the decoration on one of the Sowerby vases from 16.10.1876.
It might help to settle this issue if you are able to photograph the neck only, showing just the moulded decoration, as clearly as possible.

Just looked again at the height of this piece - seems unusually short for a jug, so assume a small cream or milk jug. Regret the backlit picture is too poor to be of help.