Same thing that makes a 1.9TDi VW more expensive than a 1.9TDi SEAT with the same engine!
And a B1&B2 are aircraft types........ and therefore Watch models.
ATCO Two....
bought it on eBay for £900 from a chap who found it too heavy to wear
Be very wary of buying anything of limp wristed types on ebay matey!
