What was found
ON START-UP, THE PILOT REPORTED THAT THE NR INDICATION WAS AT 364 INSTEAD OF 394 & WAS FLUCTUATING DOWN TO 351. BOTH THE ANALOG NRS & THE DIGITAL NRS ARC WERE FLUCTUATING & THAT THE NF HAD EVERY OTHER SEGMENT OF THE DIGITAL ARC NOT ILLUMINATED. AFTER TROUBLESHOOTING, THE ENTIRE SYS IAW MM CH 63-41-00,1-1 NO DEFECTS FOUND. ADVISED TO LOOK FOR BROKEN FINGER OR FINGERS ON THE PHENOLIC WHEEL IN THE MAIN GEAR BOX. ONE FINGER WAS FOUND MISSING. MAINTENANCE WILL BE DONE TO RETURN THIS ACFT TO SERVICE. THIS WAS DISCOVERED ON A GND RUN, 0 FLIGHT TIME RECORDED.