Other than the fact that their tokens bear the date 1875, no positive information about the history of this partnership has been located as of 11/4/2005.
The book about Christchurch token issuers, They Made their Own Money, includes the following information:
'In 1866 there were two butchers listed in the postal directory: William Gaisford, Sandyford Street, Sydenham, and G. Edmonds, 71 East Town Belt, Christchurch. The latter site was located on the corner of Fitzgerald Avenue and Tuam Street. It is possible that these were the partners in the Colombo Street business of an earlier date, but no proof has been secured to support this supposition.'
Given that their tokens were issued circa 1875, it is also possible that they became partners later than 1866.
The Canterbury Branch of the Royal Numismatic Society of New Zealand (1950). They Made their Own Money: The Story of Early Canterbury Traders & their Tokens, pp.66-67.