ACFT CLBS 1000 FT HIGH FOR CRUISE FLT.

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ENROUTE FROM SFO TO DEN ON CLBOUT ZOA CLRED US TO FL290 WHICH WAS OUR REQUESTED FINAL ALT. WE SET OUR ALT ALERTER TO FL290. BOTH PLTS RESPONDED VERBALLY AND POINTED WHEN THE ALT ALERT WAS SET. AT FL280 THE SOP CALLOUT 28 FOR 29 WAS MADE AND RESPONDED TO. I (THE CAPT) WAS THE PF. I LEVELED OFF AT WHAT I THOUGHT WAS FL290. JUST AFTER LEVELING OFF ZOA CALLED AND ASKED WHAT ALT WE WERE AT. ONLY THEN DID WE REALIZE THAT I HAD LEVELED OFF 1000 FT HIGH. THE ZOA CTLR ASKED IF WE WISHED TO CONTINUE CLB TO FL330. WE RESPONDED AFFIRMATIVELY. WE WERE CLRED TO FL330 AND CONTINUED CLB TO FL330. NO TFC CONFLICT EXISTED OR WAS CAUSED. ALL SOP'S WERE OBSERVED. THERE WERE NO DISTRS. WORKLOAD WAS LOW. SO WHY DID 2 EXPERIENCED PLTS MISS THIS ALT DEV? THIS IS MY BEST GUESS. THE ALTIMETER WAS THE OLD TYPE WITH 3 POINTERS (NON DIGITAL). SOME OF THE ACFT WE FLY ARE STILL EQUIPPED WITH THESE ALTIMETERS. THEY ARE MUCH HARDER TO READ AND INTERPRET THAN THE DIGITAL TYPE. ALSO IF THE ALT ALERT WORKED AFTER WE INADVERTENTLY CLBED THROUGH OUR ASSIGNED ALT (NEITHER ONE OF US RECALL THAT IT DID) IT DID NOT DO ITS INTENDED JOB. IT DID NOT EFFECTIVELY GET OUR ATTN WHEN WE PASSED THROUGH OUR ASSIGNED ALT. THE SYS WE HAVE GIVES US A LIGHT AND A TONE APCHING AN ASSIGNED AND SELECTED ALT AND AUTOMATICALLY GOES OUT WHEN APCHING THE ALT. IF ONE PASSES THROUGH THE ASSIGNED ALT THE SAME LIGHT AND TONE COMES ON AGAIN AND GOES OUT AUTOMATICALLY. IN OTHER WORDS THE ALERT FOR APCHING AN ASSIGNED ALT IS THE SAME AS THE ALERT FOR DEVIATING. IT IS NOT DISTINCTIVE ENOUGH TO DRAW ONE'S ATTN TO A DEV. SUPPLEMENTAL INFO FROM ACN 315422: WE HAD HEARD NO TONE FROM THE ALT ALERTER AS WE PASSED THROUGH THE ASSIGNED ALT OF FL290. THE ALERTER WAS STILL SET AT FL290. THE ALT ALERTER FUNCTIONED NORMALLY THE REMAINDER OF THE FLT.