Hi gpo746
Sorry it's taken a couple of days, I had a follow up meeting with the surgeon that did my knee and stuff to do in Berwick over the last few days.
So found the tank, flat is a bit of a relative term for these tanks, it's the flatter of the two tanks but not as flat as the flat toolbox, threads are good, tank is sound, paint is so so but has a few scrapes, no dents that I could see, when I bought it it was sealed with tape which explains the square mark around the filter /drain hole (probably to seal it for posting).
Anyway it's not going anywhere soon so have a good look, if it's what you want send me a PM,