Try https://www.watfordgold.org.uk/history/a-history-of-watford-f-c-s-history Scroll down and look for Olly Phillip’s Official Centenary History. It’s in there.
In early December 1935, Watford conceded their 1,000th League goal, February 1936, Coventry were dispatched, 5-0, with Devan hitting three in eight minutes. His second was the 1,000th scored by Watford in the League. Never seen this website....excellent