sorry, can't add anything of real use, other than to say unlikely to be from the period it's shape is suggesting, but it's interesting and a nice piece of glass.
Boat shaped salts with some sort of saw tooth or scalloped rim were one of many reproductions of Georgian table glass made during the first third of the C20 - copies of C18 glass were a big thing by, for example, Hill Ouston in the early 1930's, although I get the impression most were clear glass only.
Keith's suggestion of Thomas Webb is a possibiliy, but others apart from T/Webb did use this blue, and I would have thought finding a maker to be very long odds.
If the cutting looks to be in unusually good condition, then unlikely to be prior to the C20 - earlier cut salts tend not to survive without some indication of a hard life.