(a) a card certifying that its holder is able or entitled to work; (b) a card certifying that its holder is a member of a particular trade union; a…

(a) a card issued by an employer as proof that the cardholder is employed; (also in later use) a card certifying that the bearer has permission to…

A card entitling the holder to free meals or lodging, esp. one issued by a labour union; a meal ticket. Now historical.

British and Australian colloquial. In plural. Documents relating to an employee (esp. concerning tax and National Insurance) held by an employer…