Well, according to my copy of The History of the Birmingham Proof House the busiest year appears to be 1868 with a total of 961,459. Between then and 1885 there were only two years when the total went just under half a million per annum. There were significant peaks during the American Civil War and the Austro/German and Franco/Prussian wars. They keep very details records so I suppose someone there may know the answer. Lagopus.....