A friend of mine just gave me a 14" drum that he acquired years ago when he had a 1952 Chev 1 Ton. I have to clean it up some but it appears to never have been turned and it may be NOS. It matches an NOS drum I have with one exception. It doesn't have the cooling ridges on the outside. This is not because of rust, they just aren't there. Did GM make them without the ridges?