John H. Glenn, Jr. became the first American to orbit the Earth aboard his Mercury Atlas 6 and inside his "Friendship 7" capsule as part of the Mercury program, rocketing him into the history books as an American hero and icon. Along for the ride on that mission were 32 dollar and two dollar bills secreted aboard by the launch support crew, who signed the bills and with good luck wishes to Glenn, and then taped them around the internal wiring of the spacecraft. These bills famously were signed by Glenn and formalized flight certificates were made to prove their flown provenance. They also became subject of a Congressional investigation when their existence became known. Based on an analysis of the serial numbers of all 32 flown bills as revealed by the Congressional investigation, the majority of bills were $1 bills, with 15 or less being $2 bills.
Here is a look at the flown $2 bill in the Jefferson Museum from the Glenn flight, one of the most historic flights of the Mercury program. It is one of the first bills ever acquired for the museum.