$5 1928-E Legal Tender
with an inverted reverse error
also known as an inverted back
An error which is easy to explain, but hard to detect: the alignment of the printing on one side is upside compared with the other...so each side looks perfectly normal (at least in examples printed before 1985)...as such, even those quite familiar with US paper money such as bank tellers, cashiers, collectors and dealers are prone to overlook the mistake.. yet, when both sides are viewed simultaneously, as in turning the pages of a book, the error becomes immediately apparent.
The cause of the misalignment is embarrassingly simple to describe: after the uncut sheets receive their 1st/back printing, the entire pallet is set aside to finishing drying/'curing', a process which typically takes 24 hours or more...if the ends are transposed 180 degrees as they enter the face/2nd printing presses the misalignment occurs, with the subsequently applied overprint correctly positioned atop the 2nd/face printing, irrespectively
Inverted Backs are perhaps one of the most overlooked error types
Examples exist on both large and small size paper money, dating as far back as the series
1890—although even the Fractional Currency issues printed during the Civil War and the Colonial Currency printed before the signing of the Declaration of Independence suffered from this malady.
PCGS Fine 12