What's the story?The 6105 wasn't Seiko's first diver – that honour goes to the 6217 – and neither is it the most technically complex, but it's nevertheless the most desired and revered Seiko has ever made. The Blancpain Fifty Fathoms and Rolex Submariner had truly put diving watches on the map in the '50s, and by the '60s the Japanese wanted a slice of the action. The 6105 was arguably their best shot.Why should I want one?Because even 40+ years after their introduction, they still have amazing wrist presence. The cushion case is comfortable and a decent 44mm wide, and the dial is beautifully legible. They're also legendarily rugged, which is why so many American soldiers took them to Vietnam – for authenticity, Martin Sheen wore one throughout Apocalypse Now.What to look forSadly, loads of dead 6105s have been resurrected using all kinds of random spares and poorly made aftermarket parts, earning them the nickname of "FrankenSeikos". It's also common for them to have the case refurbished clumsily. Beware too-perfect hands and dials – genuine examples should have some pitting and discoloured lume by now – and make sure the movement and case back are original. An original strap is too much to hope for. The 6105-8000 and 6105-8009 are the first versions, with a symmetrical case shape, while the 6105-8110 and 6105-8119 have the cooler (in our opinion) case with protruding crown protectors.