BE1900D LANDED RWY 4L AND EXITED RWY 33R. EVERYTHING NORMAL ON TAXI TO THE GATE. NOTED DAMAGE TO THE L PROP ON EXITING THE ACFT. ARPT AUTH INSPECTED THE RWY AND TXWYS FOR DEBRIS BUT COULD FIND NOTHING. PROP CHANGE.

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UPON LNDG AT BOS RWY 4L ON THE VISUAL; WE LANDED AND EXITED AT RWY 33R. UPON LNDG AND CLRING THE RWY; CTLS WERE EXCHANGED BACK TO THE CAPT. DURING LNDG WE WERE AT ALL TIMES ON RWY CTRLINE AND EXITED ON THE CTR OF RWY 33R. WE WAITED FOR MD80 TO PASS R TO L AND FOLLOWED HIM TO THE RAMP AREA. WHEN WE ARRIVED AT THE GATE AND OPENED THE DOOR TO DEPLANE; I NOTICED THE PROP HAD BEEN DAMAGED FROM SOME DEBRIS. 3 BLADES WERE DAMAGED. 1 HAD DELAMINATED THE BACK SIDE OF THE PROP SO THE ACFT WAS NOT FLYABLE. WE IMMEDIATELY NOTIFIED MASSPORT AND THEY CONDUCTED A CHK OF THE AREA BUT NOTHING WAS FOUND. WE WERE AS SURPRISED AS MASSPORT BECAUSE WE DID NOT HEAR OR FEEL ANYTHING HIT THE PROP AND NOTICED ONLY WHEN OPENING THE DOOR TO DEPLANE. THE CAPT FILLED OUT AN IRREGULARITY RPT AND MAINT REPLACED THE PROP. SUPPLEMENTAL INFO FROM ACN 359966: I WOULD GUESS IT OCCURRED AT TOUCHDOWN; IE; HIGH SPD. PREFLT IN DEP CITY BGM WAS NORMAL; AS WAS THE ENRTE. NO VIBRATION; ETC; WHICH LEADS ME TO CONCLUDE THAT THIS HAPPENED ON LNDG ROLLOUT.