Three changes seem to have been made in the Type VII-C, all at approximately the same time: 1.) elimination of the bow net-cutters, 2.) elimination of the side deck extensions alongside the deck gun, with the substitution of a crescent-shaped line of round holes cut in the side of the hull, 3.) addition of the hydrophone "hammer". In order to achieve the greatest amount of accuracy in my 1/72 model, meant to depict a VII-C as it would have looked ind spring 1941, I would like to know whether all these changes were introduced at the same time, or sequentially, and, if the latter, what was the order of their introduction.