I dont have any of the larger sabers but as far as the plaque goes if its oxidizing you can prob find some jewelery cleaning solution to clean that up. honestly ive never heard of car wax being used to clean oxidation (or clean anything for that matter). Its wax, you clean the car and put the wax on as a protective coat. So it may be an idea to put a coat of wax on the plaque after you clean it as it may help keep it from oxidizing. How often depends on the enviornment you keep it in...but car waxes generally hold up for pretty long periods of time (nu-finish says to use it twice a year) so i would imagine that a coat of wax would last fairly long on a display item, especially if there is no contact with it