a reference device for cooperating with {HEAD ~ the cylindrical part} in {TAIL ~ orbital motion} and defining a checking condition of said apparatus 
a reference device for cooperating with { HEAD ~ the cylindrical part } in { TAIL ~ orbital motion } and defining a checking condition of said apparatus
OTH OTH OTH OTH OTH OTH HEAD HEAD HEAD HEAD HEAD HEAD HEAD REL TAIL TAIL TAIL TAIL TAIL TAIL OTH OTH OTH OTH OTH OTH OTH OTH