[3] Jupiter-C was used for three uncrewed sub-orbital spaceflights in 1956 and 1957 to test re-entry nosecones that were later to be deployed on the more advanced PGM-19 Jupiter mobile missile.

The recovered nosecone was displayed in the Oval Office as part of President Dwight D. Eisenhower's televised speech on November 7, 1957.

[4] A member of the Redstone rocket family, Jupiter-C was designed by the U.S. Army Ballistic Missile Agency (ABMA), under the direction of Wernher von Braun.

During first-stage flight, the vehicle was guided by a gyro-controlled autopilot controlling both air-vanes and jet vanes on the first stage by means of servos.

The Jupiter-C was part of the IRBM project, and the sequence of manufacture of the rockets (which are not necessarily launched in order, and may be uprated as solutions to technical problems are worked out in tests) was considered a military secret.

So the designation painted on the sides of the rocket was not a serial number in clear text, but employed a simple transformation cypher that the staff would be sure not to forget.