East India Company, an unusual officer’s button of non regimental pattern

The 19mm officer’s gilt button has the backmark FIRMIN & SONS, 153 STRAND has the design of the lion crest of the Honorable East India Company within an oval garter surrounded by a wreath. There are traces of the original gilt and the button is not much rubbed. The shank is a little bent. As there are no regimental marks our assumption is that this is probably a staff design although we have not seen an illustration of the pattern in any of the reference books or articles showing company buttons, although there are precious few of those.  oct8/1