Red for Red Upgrade - Is old box disabled

Hi there, We have bought a T70 on a red for red upgrade path. When I register the device it asking me which device it is replacing. Does anyone know if this impacts the existing device at all? I need to set the new one up and test it before sending out to a branch office.

I assume it probably prevents the old device from being re-registered, but thought it wise to check.

Many thanks. Alan.