Does my Z1 compact have carrier branded firmware or pure Sony?

[dieselnutjob1]

Someone gave me this Z1 Compact.  It was left in a cupboard at work apparently not working, but I found that if I stuff a thin piece of card under the SIM card that it tightens the connections enough for it to work.

How do I tell if this handset is carrier branded handset or not?

[Thommo]

Dial *#*#7378423#*#* then open Service info then Software info and post back with the Customization version number

[dieselnutjob1]

1280-7858_R2D

[_alexdon_]

Customization version: 1280-7858

Operator: T-Mobile UK (United Kingdom)

[Thommo]

If you dial the same code then open Software info the SIM lock and post the results we'll be able to let you know if your phone is carrier/network locked, available to be unlocked or hard locked to a network