what's this all about?
http://cgi.ebay.co.uk/National-12-Mug_W0QQitemZ160116664240QQihZ006QQcategoryZ90875QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
I don't know looking at this discussion group there are plenty of n12 mugs about although if they are double bottomed they might be a good investment. ::)
2 more - different design
http://cgi.ebay.co.uk/A-pair-of-National-12-logo-coffee-mugs_W0QQitemZ160116091843QQihZ006QQcategoryZ90875QQssPageNameZWDVWQQrdZ1QQcmdZViewItem