That's the RAF Pilot/Navigator issued Gen 1 Seiko. It looks like it needs a new glass/perspex and has the tell-tale marks on the caseback from being on a nylon NATO strap. I have seen these go for as much as £1,200. I suspect it will go for more than is currently bid. Seiko UK will happily service these at very reasonable cost. I still have the Gen 1 issued to me as I started advanced flying training in 1988, and a Gen 2 that I was issued with later for reasons I won't bore you with here.