Here is a photo of my base plate: Model___________3012-R
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I took my arm apart today, confirmed that I have the nylon bearing and learned how to reassemble it all. The arm tube extension seemed a bit loose, so I disassembled it and tightened it all up. In the process, I had to set it up again. This included the lateral balance mechanism. You can see from this photograph that the aft arm tube extension behind the pivot and bearing that holds the counterweight is offset to the right by about 1/4" relative to the main arm tube in front of the pivot/bearing. This is adjustable with an allen wrench allowing it to move left/right. So after one confirms vertical balance (floating the arm before applying VTF), one also does it for horizontal balance so that the arm does not float or drift inward toward the spindle or outward toward the armrest. This is all explained in the very comprehensive manual. The arm is back on the armpod , all realigned and set up, and it sounds great.
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One difference I notice is that some 3012R arms have a black arm lift mechanism and some have silver ones. Mine is black. I don't know if this designates a particular year of manufacture. Perhaps they were experimenting with style. Other than the color of the plastic, the arms seem identical.