The difference is that the more common one during the Civil War, the NA112, had the upper fluke of the anchor behind the left wing, whereas the NA113 had the upper fluke of the anchor in front of the left wing.
These types were used right up through WWII, although the NA112 type became much less common after the Civil War.(source: , by Alphaeus H.
All of us, myself included, have made mistakes in judgment with cleaning methods, but I'd like to share some of the methods and techniques that have worked best for me in the past 20 years of metal detecting. There are millions of these underground, and most folks don't give them a lot of thought. The backs of flat buttons frequently have either a maker's mark (company name) or a quality mark.
Both types of marks on the reverse of buttons are called "backmarks." Quality marks were the manufacturer's way of promoting their product.
However, the buttons in Myra's collection are not that early: they date from the 1850's.