The most important distinguishing part of your Toppy is the System ID, which determines which firmware it can run. This appears on the front panel when the power is turned on. Some cases only ever have a particular system id, while other cases may be used for more than one model. The pictures and information below will help you determine exactly which model you have.
TF5800PVR & TF5800PVRt
This is the original UK case style, available in either silver, black or (rarely) white. Models shipped before around mid 2008 will display C.456 when turned on, which corresponds to a TF5800PVR. Those shipped from 2008 onwards may have the Freeview Playback logo on the front, and display C.458. If your PVR shows C.458, then you have a TF5800PVRt. There are no other technical differences.
This model is supplied with Freeview Playback firmware. It has an HDMI port on the rear, and will display C.457 on the front panel when starting up. There’s a large silver button in the centre of the front panel, and a small power button at the left, with a blue glow around it.
This is the facelift version of the 5800. It will display C.458 on the display when first turned on, and has a blue-ringed power button in the centre of the front panel.
Note that if the main board has been replaced in your PVR, you might find that the system id changes, so you could have an old style TF5800PVR case with a newer main board that now displays C.458. In that case, you should select TF5800PVRt to ensure that you can download the correct firmwares from this site, even if it previously had a system id of 456.