Hi i have an old DMT that i bought for knife sharpening. i watched a video on You tube where a Dmt was used to set the bevel on a very dull razor. my question is this DMT is a steel plate mounted to a 1/2 inch high dark red plastic base, it came in a wooden box. does anyone know what grit it might be. and does the surface ever wear out. mine is in good shape. thanks for your help.