1921
Serial numbers on any bills are counters and a security feature. A specific serial number doesn't stand for anything except the order in which a particular bill was printed as part of a print run.
The Auto 5 speed loading feature was introduced in 1954.
It has no particular meaning. Serial numbers are counters and a security feature; they're printed sequentially so your bill is simply one of many billions.
Generally speaking, the thing that makes all bank notes different is the serial number. Each serial number is only used once, and to further make it individualized, the serial number is combined with a letter (or letters) ensuring that no two bank notes will ever have exactly the same serial numbers.
I was looking for information on a rifle with a similar serial number. armscollectors.com has a lookup feature that will help. Check out Marlin under Manufacturers Dates on the main page.
The US didn't print any bills dated 1956.Also note that it's normally not necessary to provide a bill's serial number. Serial numbers are counters and a security feature but rarely affect a bill's value.
Also, as you've seen in other postings, a bill's serial number almost never affects its value so that's not an identifying feature.
Please post a new, separate question with the bill's date and what letter, if any, is under the date. Serial numbers are counters and a security feature but rarely identify a bill for valuation.
Serial numbers are counters and a security feature but rarely help to ID a bill. Please post a new question with its date and what letter if any is next to the date.
The serial number and most times the letter on the bill.
Serial numbers are counters and a security feature but rarely ID a bill for valuation. Please post a new, separate question and include the bill's series date and what letter if any is next to the date.
The silver union star in front of the serial number on new, colour post-2004, $50 bills is a security feature of the note to make counterfeiting more difficult. A small star after the serial number an any denomination indicates that the original note had a printing error and was replaced.