As reported to the FAA. Reports are unverified, and codes are left as the FAA publishes them.
What was found
CLIMBING THROUGH 10000 BOTH CA AND FO AIRSPEED MAX LIMIT STUCK AT 260 AIR RETURN TO EWR UPON ARRIVAL CONFIRMED BOTH AIRSPEED INDICATORS STUCK AT 260 KNTS. CYCLED S591 VMO/MMO SWITCH MAX AIRSPEED LIMIT INDICATOR CKED NORMAL. SECURED SWITCH WITH SAFETY WIRE.