How to see if T420 has dedicated GPU?

[Quicklite]

Bought a T420 the seller said there was 4200M.

So far when I try to install NV driver - it says its not recognised.

I can only see integrated option in the device manager.

Is there a way to see for sure if there the machine has Nv graphics?

[RealBlackStuff]

Put the 7-char. TYPE (from the bottom label) in the MTM link at the top of this page.

[Quicklite]

It's a CTO custom built version.

Basically - under bios > display - there is only Thinkpad LCD - can't see any NV options.

When I try to install the driver via Lenovo site it tells me to restart as the installation starts?

Does that mean there might not be dGPU on this laptop?

[RealBlackStuff]

Go here: https://support.lenovo.com/us/en/partslookup and put in your S/N (without the dash) and maybe the first 4 TYPE chars.
Then compare the motherboard/planar P/N or FRU from the parts list with the HMM to find out what you have.