What 1950 us 10 dollar bill has no series?

Answer 1

Actually, it does have a series - 1950, or sometimes "1950 plain".

Series dates and letters on US bills are peculiar. The date doesn't indicate when the bill was printed, but instead indicates when that particular printing run was started, hence the term "series date" instead of "printing date".

To complicate things more, the first set of bills for a given series date has no letter. A letter is added only when there is a more minor change that doesn't warrant a full new series. That is, the letter "A" refers to the second set within that date, "B" is the third, and so on.

If that isn't confusing enough, the criteria that determine when a new series starts have changed over the years. For many decades series dates would be changed only when a bill was redesigned. The series letter would be incremented if either a new Secretary of the Treasury or new U.S. Treasurer was appointed. That practice led to the odd situation of 1935-series $1 bills being printed as late as 1965, with series letters extending up to H.

In 1974 the Treasury decided that a new series date would be used if a new Secretary of the Treasury was appointed or there was a substantial design change. The series letter would be changed only if a new Treasurer took office. As a result, series dates now change much more often and series letters rarely go beyond B.

Of course, even this policy has its exceptions. For example, the current gray and purple $5 design was introduced without a corresponding date change.