small time American currency collector here . Old from the 50s , 60s and 70s and before it became monopoly money is what i collect and some can still be found . Course i also collect any USA paper money or silver coin i can find but finding is hard to do . So nowadays i just collect star notes and similar that really have no value more than the actual denomination . I did most of my finding of 50s , 60s and 70s bills when i cashed my paychecks , probably in the 80s and 90s when i became interested . I reasoned that i could take a nice unfolded 50 dollar bill or whatever bill , put it aside and if nothing else it was still a 50 dollar bill ready to be spent if needed .