G-ALVG (not -GV) was the original D.H. Comet prototype which was demonstrated at the first Farnborough show in ’49; and G-5-2 was the second Comet prototype, although you say it appears to be a Vampire type aircraft, which is a bit puzzling.

This thread will probably explain your confusion over the ‘G’ numbers, it did mine!

http://forum.keypublishing.co.uk/showthread.php?t=78806