but on the "Bundt Cake" rims all the dimensional data is forged into the BACK of several of the webs between the spokes, so unless you're really clever with a tiny mirror, you have to remove the wheel and brush off a whole lot of asbestos dust to read it. Before 1980 or so, you will find the width there, the M-B part number, and a production date on the mounting face, but not the offset (ET) number, so you have to measure or find someone with a M-B parts book who's willing to take the time to correlate the part number to the size information on Merc. spec. books. Steel rims are probably stamped in the area between the lug bolt holes.