I have one of these, and other than it having a little better tail than most, I think you have one of the Webb Exhibition pieces. These were done for the Franco British Exhibition held at the White City in Shepherd's Bush, London. Webb built a glass house for the exhibition. There is one shown on pg. 24 of ART, FEAT AND MYSTERY, THE STORY OF THOMAS WEBB AND SONS, GLASSMAKERS, by H W Woodward. I think there is also one shown in Hajdamach's book (most likely the same one). The one in the Woodward book shows an original box. By the way, I have seen examples of this piggy sell for upwards of $150 US. Mine has part of one ear missing, and it still cost me $50 US. That full tail would make it bring the $150 or more if it popped up on FeeBay
Mr. Vaseline Glass
(Dave Peterson)