Green’s Dictionary of Slang

Mary Slessor n.

[Mary Slessor (1848-1915), a missionary, whose portrait was printed on the reverse of Clydesdale Bank £10 notes in 1997]

(Scots) a £10.00 note.

[Scot]L. McIlvanney All the Colours 89: Ten minutes later, Mary Slessor still in hand, I needed to piss.