I forgot what year, but the serial number.Co2md1usf8j2 EMC 2638 Model A148 100-240V 50-60hz. Hard for me to see the o could a 0.It is firmware locked. What year machine do you have? if it's 2010 or older - you can remove some RAM and give it a few PRAMS which will remove the firmware lock - else it'd require other tools to remove via firmware chip