2015 models and no serial number in dump?

I've come across 4 or 5 2015 model Airs now that have no serial number in the BIOS dump file, yet the boards *do* have serial numbers when booted into OSX. Where is the serial number stored if it's not in the BIOS dump? Is it in the file, encrypted? When searching for "ssn", "hwc" and "serial", nothing returns that shows a serial number.

Thanks!

dosdude and i were tinkering with serial numbers, i'm convinced the serial is stored elsewhere.

changing the serial# in the EFI and booting from an AppleHardwareTest usb, it reports UNKNOWN serial#.

changing the serial# in the EFI only affects the system profiler. need to change everywhere including the bottom lid lol

On 2014 MacBook pros I've had where serial number was changed, I did so in the efi dump. I opened the dump with a notepad c++ program, search hwc and the original serial is shown and edited to new. Re write the efi with modified dump and it shows new serial in hardware info and also eliminated the apple device enrolment profiles that after iCloud removal and fresh OS X install were still linking to the machine with the old serial left in place.
I've just done a mid 2015 mbp and modified serial in the same manner and it was visible in the dump the same way as the 2014 model.
Am I right in thinking you've not been able to view the serial on a 2015 machine??

the ones that stand out in my mind are 12" MacBooks

Ah ok...no dealings with a 12" as yet