Indexed Concentric Rings, Dual Extruder Offset Calibration

This is a remix of the Concentric Ring Extruder Offset Calibration object. I enlarged it slightly and added an index marker so the print can be removed from the bed without losing its orientation. The index mark should point toward the corner.

After loading the two parts, assign each to a different extruder, then CENTER both parts on the bed to create the merged object. The inner ring should fit perfectly within the outer ring. After slicing and printing, measure any misalignment and adjust