100 Pounds Royal Bank of Scotland

The Royal Bank of Scotland's £100 note occupied a rarified corner of Scottish commercial banking — a denomination that rarely left bank vaults and moved almost exclusively between businesses, solicitors, and estate transactions. Notes of this value were handled by tellers who knew their counterparties by name. Retail circulation was essentially nil.

Pick 320 spans nearly ninety years, during which the note's printed design changed incrementally rather than wholesale — a deliberate conservatism that made forgery detection easier for the institutional users who actually handled them. The watermark security relied heavily on the quality of the paper rather than complexity of the marking itself.