Unit Serial Number

[Cloverjo]

I have bought insurance for my son's laptop while he is at university. The insurer is asking for the unit serial number. My son has told me the three different numbers that are on the bottom, but we don't know which is the relevant one. They begin :
E1-572-340......[other figures], the first six figures are the model number
S/N:NXMSEK......[other figures]
SNID:.... Etc
Can anyone help please?

[Buenchico]

Guess what S/N stands for . . . ?
;-)

[Cloverjo]

Grr..
Thanks, Buenchico.

[VHG]

Buenchico, why do you only answer the difficult questions ;-)