My Marine Chronometer. Hugely expensive when new and accurate to +/- one second per month, mine doesn't appear to ever have been polished and comes with its original box, chronometer papers and plastic wallet they came in.

It's my stealth watch, people think it's an ugly old quartz of no value and it attracts no attention whatsoever (only from friends who know I like watches and are surprised to see me wearing something like that. It's clearly been worn - but not abused - and the bracelet is nice and relaxed, not virtually inflexible like the one on my fully restored stardust dial MegaQuartz

The Marine Chronometer cost a lot of money in 1976, something like three times the price of a Speedmaster. Jacques Cousteau wore one

It's currently at STS, Omega's UK vintage watch specialist, having the dial straightened. It's an ugly thing but I love it and can't wait to get it back and on my wrist.