Thank you very much for your help which seems to fit as I take a magnifying glass to the units.
I guess I was quoting model numbers. The two 4FL6 are indeed GO 6000 with serial numbers that start with QQ. When powered up these have "trouble accessing Tom Tom services". I will assume these are to be scrapped.
The GO Premium is still in it's box; I will leave it there and assume it's current. Sadly Rob never had the chance to use it.
The other two are slightly larger than the QQ ones and look identical. Serial numbers B44233V00589 and ZW4041V00378. I think they are more recent because the USB connector is oval and not flat on one side like the QQs. These two pick up a satellite signal and function ok. Maybe the serial numbers are different because I'm in the UK?
I will be grateful for any comment.
Derek
Your two QQ ones are a bit dated. What the devices are telling you is that they aren't making a successful cellular connection back to TomTom for things like traffic data. However, I believe you'd find that they also have a Bluetooth interface that could be used to get traffic data were you pair up a phone as a Bluetooth tethering device to transfer the data from TomTom to the GO 6000.
The B44 is indeed a quite recent GO model ... a nice 7" unit. It could be any one of several 'sub-models' depending upon which firmware and maps were loaded. There's the Expert Plus (truck), Exclusive (Car and Camper) Superior (Car) versions. You can tell which it is by firing it up.
The ZW is one step back in time from the B44, and is also a nice 7" device. Again, which sub-model can't be known directly from the serial number, and again, it's a function of firmware and maps. These will be either the Expert (Truck), Camper Max (Car and Camper), Discover (Car) or Exclusive (Truck and Car and Camper).
The ZT in the box (Premium X) is, with regard to age, actually in between the old QQ devices and the newer ZW and B44 devices, but hang onto that one for posterity. I believe it's the last device TomTom has or will ever make that has a cellular service connection. I'm surprised your brother didn't fire that one up much sooner. A new owner may have to contact TomTom to get service initiated on that one since it sounds like it's never been out of the box and it's been a while. After a couple of years, TomTom drops the account for SIM support, and one would necessarily have to ask to have it reinstated.