"Half a ton" was exactly what the captain said in his first announcement to us just before we disembarked - whether this was said for effect or purely a generalisation I do not know. However there are two points to be made on this; a. I do not recall smelling an excessive amount of avaiation fuel (a smell I am perfectly familiar with from my offshore helicopter and fixed-wing flights), and b. there was no visible lake beneath the wing, more a sizeable puddle.
With regard to the signing off of the Tech Log there was a man who appeared to be an engineer who entered the cockpit for a moment before the departure.
The aircraft was indeed a 737, 700 series.