MLG ACFT CLRED TO DSND TO 11000 FT BY ARTCC RADAR CTLR; FLC READ BACK ALT AND DSNDED. WHEN CHKING IN WITH TRACON THEY WERE TOLD THEIR ALT WAS SUPPOSED TO BE 12000 FT BUT NO PROB.

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GIVEN XING RESTR TO CROSS TRISH INTXN AT 11000 FT. FMS ACFT AND TRISH INTXN NOT ON FMS MAP. LOOKED ON AIRWAY CHART TO CONFIRM POS OF TRISH INTXN; ENTERED IT IN FMS; AND BEGAN DSCNT. CALLED BAL APCH 'OUT OF FL180 FOR 11000 FT.' BAL CTLR ROGERED. LEVELED AT TRISH INTXN AT 11000 FT. CTLR THEN ASKED TO CONFIRM ALT. REPLIED; 'LEVEL 11000 FT.' CTLR SAID WE WERE CLRED TO CROSS TRISH INTXN AT 12000 FT. NO TFC CONFLICTS NOTED. BAL CTLR SAID TO REMAIN AT 11000 FT. I CALLED APCH CTL AFTER LNDG IN DCA. THEY SAID NOT TO WORRY ABOUT IT; BUT I THINK A NASA RPT IS IN ORDER. WERE DISTR BY LOOKING UP TRISH INTXN WHICH WAS NOT IN FMS. DID NOT IMMEDIATELY DIAL IN XING ALT IN AUTOPLT ALT WINDOW. EVEN THOUGH WE READ BACK 11000 FT AND CALLED 'OUT OF FL180 FOR 11000 FT;' WE DID NOT ASK FOR CONFIRMATION OR CLARIFICATION. THOUGHT WE HAD CROSSED TRISH INTXN AT THE ASSIGNED ALT. HAD BRIEFED TO BE EXTRA CAUTIOUS WITH ALT ASSIGNMENTS SINCE SEVERAL PLTS HAD DEVIATED FROM ASSIGNED ALTS IN LAST YR. NOT SURE WHAT THE ASSIGNED ALT REALLY WAS; IE; WHETHER WE WERE WRONG OR CTLR WAS WRONG.