The firm of Whittingham and Percival was based in Pendleton, Salford, and lasted for a few brief years in the latter 1870s.
Here are some photos of an uncommon clear glass salt from the works. It is 3 inches across x 1.7 inches high. There is a registration lozenge for 6 June 1876 to the interior base. The exterior sides have decoration of repeating oval panels Ė diamonds in one, and horizontals in the next and the underside of the base has an impressed star.
A batch of Whittingham & Percival designs (RDs 301058 to 301067) were registered on the same date, but only five of them (RDs 301063-301067) were for salts.
NeilH has photos of two of the salts (RDs 301063 and 301067) on his Manchester glass website at https://sites.google.com/site/molwebbhistory/Home/registered-designs/other-manchester-registrations-designs-by-name/other-manchester-registrations-u-to-z
so, as this salt is different, it must, by elimination, be either RD 301064, 301065, or 301066.
I will draw Neilís attention to this post and see if he can provide a precise identification for the RD number of this particular salt.
(Permission for re-use of these image on the GMB granted by smartie5166 )