Suntour freewheel sprocket spacing gauge. "Regular" refers to 5-speed and normally-spaced 6-speed freewheels. "Ultra" refers to the Ultra-6 freewheel, which introduced the notion of stuffing 6 sprockets into the same space traditionally taken by a 5-speed freewheel. Probably applies to other, newer "narrow" spaced freewheels (and possibly cassettes) as well.

No idea what the black wafer is for. Does it have anything stamped on it?