I think that paper money featuring allegorical people has a truly old and classic feel, and I believe that this will influence the value of collectable paper money down the road. For this reason, I have been making purchases related to this sort of banknote which, quite often, can be acquired quite inexpensively. Case and point: a Peruvian banknote from 1956. My latest acquisition is that of p77, which is a 10 Soles de Oro banknote from 1956. The front of this note features a seated allegory of Liberty holding a shield and staff at center. These banknotes are still available in UNC condition, though this one is in VF condition. I bought it for $2.74.
Again, I consider these great investments, though I believe it will be 20+ years before these are truly valuable. If you’re planning on being around in 20 years, stock up!