2 Dollars United States Treasury, 'Rainbow Note'

The "Rainbow Note" designation comes from the deliberate use of multiple ink colors across the face — a direct response to the counterfeiting epidemic that plagued earlier monochrome Legal Tender issues. The Treasury and ABNCo were experimenting with chromatic printing as a security measure, and the 1869 series was the most visually aggressive result of that effort. It did not last long; the public found the notes garish and difficult to authenticate by feel, and the series was quietly retired in favor of more restrained designs.

Legal Tender status meant these circulated without gold or silver backing — a politically contentious fact in 1869, when the question of hard money versus greenbacks was still driving congressional fights left over from the Civil War financing era.