Help: MUSIC MAN AXIS – Where to find the serial number

I am new in this forum so first I would like to say hello to everybody!

I have just purachased an AXIS (usend but mind conditions) but I cannot find the serial number…I have checked both on the back of the headstock and on the bridge plate but without success.

Can you help me on this?

I need it to register the guitar and to find out the year it was manufactured.

Thank you so much!