always possible that sellers who aren't overly conversant with current thinking as to attribution, might simply pick on names that are historically known to have produced vast quantities of pressed glass. On the other hand it probably doesn't take much internet digging to at least see that for some quite long time Sowerby was assumed to be the maker, prior to the revised thinking of Moore.
If the clear example here is genuinely c. 1880, then certainly a very interesting find, and who knows - perhaps unique even.