The figure of 300 employees for Reilly in 1881 seems a very high figure especially in relation to 140 for WW Greener. I cant help but wonder if there is some puffery in this self reported figure. If he really did employee 300 workers he would have had to have made thousands of guns a year to cover this overhead. Perhaps he had other manufacturing business and lumped all his employees under one banner for some reason?
If we take the figure of 300 as correct the evidence of the output will be found in the day proof ledgers of Worshipful Company of Gunmakers proof house. These ledgers and archive of the London proof house can be viewed in the Guildhall Library in Central London. I have spent a many days there myself looking at the period from 1914 to 1945. If Reilly made guns in London the evidence will be in these day books. If Reilly did not make guns there will not be any entries under his name.
Regards
Alan
