This piece, with a mei purporting to be that of Yokoya Sōmin, has a composition that very closely matches a composition given by the Imperial artist Unno Bisei II ( 1864-1919. and from Mito)

He advises shakudo in 10 parts and silver in 3 to 4 parts. There’s obviously room for some variation here as the shakudo alloy’s gold content is not specified but a narrow range of possible compositions can be estimated quite easily based on typical shakudo alloys of the period.

Cheers George, yes , the mei is somewhat dodgy but I thought it’d be a fun exercise for some :-)

https://www.militaria.co.za/nmb/topic/20642-yokoya-school-piece-under-investigation/