WRONG CIRCUIT BREAKER COLLARED BY MAINT.

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ON PREFLT; FOUND THAT PREVIOUS MAINT ACTION REQUIRED FOR MEL OF THRUST REVERSER HAD PULLED AND COLLARED WRONG CIRCUIT BREAKER; HAD PULLED CIRCUIT BREAKER BELOW LABEL INSTEAD OF ABOVE LABEL. I HAVE FOUND ON MANY OCCASIONS THAT LABELING OF F-100 CIRCUIT BREAKER PANELS AND MANY OTHER ACFT CAN BE VERY CONFUSING. SUPPLEMENTAL INFO FROM ACN 307276: WHILE COMPLYING WITH A SPECIAL PROC REQUIRED BY AN ITEM BEING PLACED ON THE MEL STATUS; MECH PULLED AND COLLARED THE INCORRECT CIRCUIT BREAKER. OBVIOUSLY THERE ARE 2 CONTRIBUTING FACTORS TO THIS ERROR: INATTENTIVENESS BY THE MECH (TIME PRESSURE?) AND CONFUSING LABELING OF CIRCUIT BREAKERS. THE ERROR WAS MADE BECAUSE IT WAS NOT READILY APPARENT IF THE CIRCUIT BREAKER LABEL IS LOCATED ABOVE OR BELOW THE CIRCUIT BREAKER. CONSEQUENTLY; THE CIRCUIT BREAKER BELOW THE SELECTED LABEL WAS PULLED AND COLLARED; WHEN ACTUALLY THE CORRECT BREAKER WAS ABOVE THE LABEL. WHILE THE PREFLT CHK DID DETECT THIS ERROR; A LESS THOROUGH PREFLT WOULD HAVE ALLOWED IT TO GO INTO SVC. 'CHK; DOUBLE-CHK; THEN CHK IT AGAIN.'