The date is too early. Prosser was in business from about 1844-1883. I believe he was an ex-Bevington man -certainly his organs have a Bevington look about them, apart from the milled edges on the metal pipes which are common on Bevingtons because of the firm's particular type of casting bench.
Apart from working under his own name, Prosser supplied organs for Chappell & Company, the music publishers. Ashbocking, Suffolk, is an example, and there is an identical example at St. Paul's, Harbour Grace, Newfoundland.