ZDV QUESTIONS A320 FLT CREW AFTER OBSERVING AN ALT 1000 FT BELOW A BLOCK ALT ASSIGNMENT DUE TO TURB. FLT CREW INSISTS THE LOWER ALT WAS PART OF BLOCK ALT ASSIGNMENT.

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WE WERE WBOUND ENRTE FROM JFK TO OAK. WE WERE ABOUT 1/2 WAY INTO THE FLT AND EXPERIENCING CONTINUOUS LIGHT TURB AT FL370. ALTHOUGH THIS WAS AN EBOUND ALT; IT WAS REQUESTED AND SUBSEQUENTLY APPROVED BY THE PREVIOUS ENRTE CTLR. IT WAS REQUESTED AFTER CONSIDERING THE ACFT PERFORMANCE CAPABILITY; AS DETERMINED BY THE FMS. EARLIER WHILE CRUISING AT FL350; WE ENCOUNTERED A SIMILAR CHOPPY RIDE. THE RIDE AT FL370 BECAME CHOPPY PRIMARILY DUE TO AN OVCST LAYER WHICH COINCIDED WITH OUR ALT. I AGAIN CHKED THE ACFT CAPABILITY; AND SAW THAT WE WERE STILL UNABLE FL390. WE REQUESTED A BLOCK FROM FL350-FL380. THE CTLR THEN ASSIGNED BLOCK FL350-FL390; AND EXPLAINED THAT SHE COULD NOT ASSIGN FL380. AS WE FLEW WBOUND; VARIOUS ALT CHANGES WERE MADE FOR PAX COMFORT/TURB AVOIDANCE. APPROX 120 NM E OF DEN; I DSNDED TO FL360 KEEPING US BELOW A LAYER. UPON REACHING LEVEL AT FL360; THE CTR CTLR REQUESTED US TO 'VERIFY ALT.' I RESPONDED LEVEL AT FL360. SHE THEN STATED THAT WE WERE ASSIGNED FL370-FL390. I CHALLENGED THE CTLR; AND ASSERTED THAT WE WERE ASSIGNED A BLOCK FROM FL350-FL390. SHE DISPUTED THIS; AT WHICH POINT WE REQUESTED A NEW BLOCK OF FL350-FL370. THIS WAS SUBSEQUENTLY ASSIGNED; AND WE CONTINUED AT FL360 UNTIL A CTLR CLOSER TO OAK ASSIGNED A DSCNT TO FL350. WHILE I MAINTAIN THAT WE WERE GRANTED A CLRNC FROM FL350 TO FL390; I CANNOT CONFIRM IT WITHOUT A REPLAY OF THE TAPE. IF THERE WAS A DEV FROM THE CLRNC; IT MAY HAVE BEEN A COMBINATION OF LATE HR ( DOMICILE TIME); DISTR (TURB); AND HEARBACK EXPECTATION. THE CTLR DID NOT HAVE ANY INPUT AFTER THE REVISED CLRNC WAS ISSUED; SO I BELIEVE THAT A TFC CONFLICT WAS NOT AN IMMEDIATE THREAT. IN THE FUTURE; I PLAN TO BE MORE VIGILANT WHEN REQUESTING BLOCK CRUISE ALTS; AS IT IS OUT OF THE NORM FROM ROUTINE FLT OPS.