Hi Graeme,
A little info: Wakefield and Co are listed in Birmingham UK Gunmakers list. They were at 10 Whittall Street between 1897 and 1900. No other info is listed. The 9mm approx cal is likely .450 so I would expect that the cal is actually 577/450. Is you can get hold of an old catridge in this cal, try it in the chamber, BUT DON'T FORCE IT, and DON'T FIRE IT> Simply to check the calibre if you feel the need.
Stu