This is far more interesting.
At the bottom of the envelope it reads C/B 'Moon' Colln. C/B usually refers to Carlyon- Britton and Moon was a collection sold at Sotheby 7th May 1901. Fortunately I have P W P Carlyon-Britton's catalogue of the Moon sale which has a note, bought at the sale by Ready (a dealer) and the lot was purchased from Ready. So, you have made a good start with a provenance of J E Moon lot19, Sotheby 7/5/1901, this the last coin of seven in the lot (sold for 19 shillings). This passed to P W P Carlyon-Britton and the coin was sold in the second portion of his sale 20-24th November 1916, lot 1072, where it was the second coin of 3 (referenced to Moon). I don't have the buyer of this lot to hand, nor have I tried to go back into the 19th century, or forward from 1916. But it's a start!
The Hildebrand 4016 reference suggests a timing in the first half of last century. This ref. was used in the 1916 catalogue.
Anything written on the back of the ticket? I did wonder if the 76 in a circle was a Lingford reference, despite the ticket being square. The B is a good match as is the M of Moon, and he also used Rx ligated to signify the reverse. If it was ex Lingford, I would expect to see the acquisition details on the back of the ticket.
There you go, I 've just added a few quid to its value.