There is a split ring around the shaft, if someone hasn't already removed it and lost it. Dual made a little tool that you could slide down the slot and expand the ring with, but a thin screwdriver will work.
The scuffing is probably the paper ring with the strobe markings on it. When the original glue dries out, they sometimes begin to fall off and parts of them drag. When I got my 1229 the paper ring was just lying there under the platter. For some reason it never read right when I temporarily taped it back in place, so I left it off and use a platter-top strobe disk to check speeds.
The 1229 owners manual and service manual are both downloadable from the library here. The info about that tool for the split ring is in the owners manual I believe.
In addition to all of the great info on Duals here at vinylengine, it is often worth searching the Dual turntable posts at the AudioKarma forum, too. There are many Dual-holics over there, and a couple of very experienced technicians too.