1917 7 Digit Dollar Bill

Hi, thank you for the welcome! Unfortunately, I do not have a photo. This is a US note, series of 1917. The serial is T5871801A.
My father kept it for years, and I am sure it initially was my grandfather's, who kept if for years. I am trying to figure out why it had been kept all of these years, and the only thing I see on it that seems out of line is the serial number. There is some reason why they kept it.
Thanks for responding

Yes, in the large size era, leading zeroes were not used. Another quirk of the large size notes was that, when the 100,000,000th note was printed, the tally would be kept in the actual serial number, ex. A100000000A. Unlike the non-leading zeroes, this rule would continue in many areas as late as the early 50s, when all notes converted to the rule that notes could only reach 99999999, with the 100,000,000th note replaced with a star note. This would later be altered again, late in Series 1974, to 99840000, and then again late in Series 1981 to 99200000, and once again late in Series 1988 to the 96000000 maximum used for all denominations except $50s and $100s, which still have SNs going up to 99200000.

http://www.uspapermoney.info/general/number.html
This page goes into more detail on what was posted above.

Yes, thanks for that Calzone.