ALTDEV CAUSED BY A VERY LOW ALTIMETER SETTING.

Narrative

CLRED TO DSND TO 17000 FT MSL. I WAS BUSY FLYING THE AIRPLANE AND MISSED THE RADIO CALL FROM CTR GIVING THE ALTIMETER SETTING. I ASKED THE CAPT FOR THE SETTING. I HEARD 'XX.38.' UNSURE OF WHAT THE FIRST 2 NUMBERS WERE; I JUST ASSUMED 30.38 AND PUT THAT SETTING IN THE ALTIMETER. THE CAPT ALSO PUT A SETTING IN HIS ALTIMETER; IE; I SAW HIM MOVE HIS HAND TOWARD THE ALTIMETER. NEITHER OF US MADE A '1000 FT ABOVE' CALLOUT. AT ABOUT 17500 FT ON MY ALTIMETER; I ANNOUNCED 'LEVELING AT 17000 FT.' THE CAPT SAID 'WE'RE LEVELING AT 16000 FT; GET BACK UP TO ALT.' I CLBED TO CORRECT ALT. NO TFC ON TCASII OR OBSERVED. NO CONFLICT RESULTED. CTR MADE NO COMMENT ABOUT THE INCIDENT. THE FAULT WAS MINE FOR NOT SETTING AND VERIFYING THE CORRECT ALTIMETER; FOR ASSUMING 29.38 AS BEING UNREASONABLY LOW ALTIMETER SETTING AND JUMPING ON 30.38. I WENT THROUGH THE MOTIONS OF THE DSCNT CHKLIST WITHOUT CALLING FOR IT; AND THE CAPT WAS TOO BUSY WITH RADIO CALLS AND ATIS TO XCHK MY SETTING. HE MISSED THE '1000 FT ABOVE' CALL WHICH WOULD HAVE BEEN CORRECT ON HIS ALTIMETER. I DID NOT XCHK HIS ALTIMETER AT ANY TIME -- MERELY NOTED HIS SETTING SOMETHING BY MOVING HIS HAND AND ASSUMED WE HAD THE SAME NUMBER SET. I NOW DO A DSCNT CHKLIST BEFORE 18000 FT MSL AND PAY MORE ATTN TO THE XCHK. CALLBACK CONVERSATION WITH RPTR REVEALED THE FOLLOWING INFO: THE RPTR FLIES THE B-767-300 FOR A MAJOR UNITED STATES ACR. AT THE TIME OF THE INCIDENT; 'WE WEREN'T PAYING ATTN TO EACH OTHER.' AT NO TIME DID THE CTR SAY ANYTHING LIKE 'ALTIMETER SETTING 29.38 LOW.' APPARENTLY THIS IS STANDARD PROC IN ALASKA AND CANADA WHERE THERE ARE MORE WILD SWINGS IN ALTIMETER SETTINGS. THE FO 'JUST JUMPED AT CONCLUSIONS' AT A MORE NORMAL SETTING OF 30.38. ARTCC DID NOT SEEM TO NOTICE THE TRANSGRESSION AS NOTHING WAS SAID. THE FO IMMEDIATELY CLBED WHEN HIS CAPT NOTICED THE ERROR.