Not thick at all!  We all have to learn from the beginning  

Yeah newer ones are LED.
Sorry, the letters denote the revision number, for example yours is: 1T0035680B.   Q, R, S etc would be 1T0035680Q, 1T0035680R, 1T0035680S and so on!
Same unit has been revised soooooooo many times over the years, which is great  

I have a 1T0035680Q in mine with the standard 2007 CAN-BUS gateway and I've left it at Gatwick for 2 weeks, no problem, started on first turn!