I can't give you the exact date for the use of metal grometts but not many were used in the CW. The only widespread use of metal grometts in the CW was those used in Federal rubber blankets. Very few large grometts are found in CW sites but in Federal sites the rubber blanket grometts are found quite often. The common union dog tent had sewn grometts as well as the wall tents. I suspect tent flys were of similar construction. I have some oil cloth grometts shown on the following page.