The Banco Nacional Ultramarino served as the note-issuing authority across Portugal's overseas territories rather than the metropole itself, and by 1959 was still printing for multiple African and Asian jurisdictions simultaneously — which is why De La Rue maintained distinct plate sets for each territory's issues. The 600 Escudos denomination is an unusual unit, not part of a conventional decimal or dyadic series, and its selection likely reflected a specific monetary-supply calculation rather than any standard progression.
P#45 is scarce in higher grades; the paper stock used across this BNU series is known to brown and soften under tropical storage conditions, which was the practical reality for most of the currency's working life.
The Banco Nacional Ultramarino served as the note-issuing authority across Portugal's overseas territories rather than the metropole itself, and by 1959 was still printing for multiple African and Asian jurisdictions simultaneously — which is why De La Rue maintained distinct plate sets for each territory's issues. The 600 Escudos denomination is an unusual unit, not part of a conventional decimal or dyadic series, and its selection likely reflected a specific monetary-supply calculation rather than any standard progression.
P#45 is scarce in higher grades; the paper stock used across this BNU series is known to brown and soften under tropical storage conditions, which was the practical reality for most of the currency's working life.