Green’s Dictionary of Slang

pound-note adj.

pompous, affected, pretentious; upper-class .

1922		‘J.H. Ross’ Mint (1955) 72: I dared not, with my pound-note accent, fall down and fail in a job. [Ibid.] 93: My bookish accent (pound-note talk). [Ibid.] 162: Pound-note speakers, men who were book-learned and of posh trades.
1936		J. Curtis Gilt Kid 63: Her pound-noteish voice both annoyed and amused the Gilt Kid.
1956		J. Curtis Look Long Upon a Monkey 71: What was he getting at in his cold, pound-noteish voice.
1958		F. Norman in Vogue Oct. in Norman’s London (1969) 30: They [...] started rabbiting to each other about one thing and another with right pound-note accents which were very loud.
1961		J. Sparks Burglar to the Nobility 135: ‘Constable,’ I said, very solemn and in my best pound-notish voice.
1962		F. Norman Guntz 99: Julian which is a pound note name no matter which way you look at it.
1979		F. Norman Too Many Crooks Spoil the Caper 29: You’re a sucker for a pound-note accent.

In compounds

pound-note man (n.)

(Aus.) a wealthy individual.

1950

S.J. Baker in Sun. Herald (Sydney) 8 June 9/1: ‘Motza’ means a lot of money; a ‘big note man’ or ‘pound note man’ is a wealthy person.