The Art Union of London was set up in 1837 as an organisation to distribute works of art among its subscribers by lottery (source: wikipedia). Subscribers paid a small fee each year to earn the chance of winning an art work which the Union had bought. The prizes typically included medals or bronzes, but also other art work like statues, prints and illustrated books. Sometimes these pieces appear at auction such as a cast iron tazza dated 1851 which was sold at Christies.
Interestingly, in 1896, the Art Union of London had an interest in repousse metalwork since one of the prizes was an electroplated repousse book cover dated 1896 by Miss M.Lilian Simpson.
It seems quite possible (to me at least) that John Pearson, possibly on behalf of the Guild of Handicraft, donated metalwork to the Art Union of London, although I am not aware of any documented link. The charger below, however, was recently sold at auction which is inscribed, on the back, ‘The Art Union of London’.
Interesting the dimensions of this charger – 39cm – are the same as the charger in the earlier post dated 1889 which is signed and dated. Stylistically, it seems to me to have many of the hallmarks of early work by John Pearson, in particular the focus on more natural decoration rather than wonderful creatures (compare, for example, the copper box dated 1891).