Funny story- - - -I was in a local welding supply store when a customer asked for some "eleven-oh-nine" welding rod. When the counterman told hin there was no such rod number, he argued that he had been using it for years. To get "1109", all you have to do his hold a piece of "6011" rod upside down!
Jerry
Kinda like a 710 cover on an engine...