The technical term for this error is a missing third overprint. However, most people just call these missing serial number notes. This misprint affects the green seal, green serial number, black federal seal, and black district letter.
Bills with missing serial numbers and seals sell for about $100 in circulated condition. The same error in perfect condition will be worth closer to $300. Perfect condition implies that the bill has never been folded and it is brand new.
This error on something like a silver certificate, legal tender, or two dollar bill can command a premium beyond the range stated above.