If you have a 1882 $20 bill that looks like the note pictured above then you either have an 1882 $20 date back national bank note or an 1882 $20 value back national bank note. Date backs have 1882 1908 written on the back of them. Value backs have Twenty Dollars written on the back of them. Value backs tend to be rarer. However, most are usually fairly common. These types of bills were printed by hundreds of national banks from towns all across the country. Some are very rare, some are very common. You need to talk to an expert in order to truly know what yours is worth. The design is very similar to the series of 1882 brown back.
If you have a blue seal note as pictured above, then we would strongly encourage you to send us a picture of it. If you have a rare variety then it could be worth thousands of dollar and we would be a very interested buyer.