As of 06/2010, a 1928 D $2 red-seal United States Note retails for $5-$12 in circulated condition. A nice uncirculated one might bring $45 or more.
Red Printing
All 1928 U.S. $2 bills have red printing, indicating that they are a form of currency called United States Notes. U.S. Notes were very similar to the current Federal Reserve notes in that they weren't backed by gold or silver in the Treasury. U.S. Notes were issued up till the 1960s. Because there was no monetary difference between the 2 forms, U.S. Notes were phased out in favor of Federal Reserve Notes to save on printing costs.
Serial Numbers
A bill's serial number is a counter and security feature but rarely affects its value, nor does it help to readily ID a particular bill. The date, condition, and whether there's a small letter next to the date are much more important.
The green seal indicates that your bill is a Federal Reserve Note. All 1928 B $20 bills were printed as FRNs. Please see the question "What is the value of a 1928 B US 20 dollar bill?" for more information.
The green seal indicates that your bill is a Federal Reserve Note. Please see "What is the value of a 1928 D US 5 dollar Federal Reserve note?" for more information.
Your bill is called a United States Note rather than a promissory note. There were eight different subseries within the 1928 series date; please see the question "What is the value of a 1928 US 2 dollar bill?" for specific information about values.
The green seal indicates that it's a Federal Reserve Note. Please see the question "What is the value of a 1928 US 5 dollar Federal Reserve Note?" for more information.
Could you check your bill again? A red seal would indicate that your bill is a United States Note; the first $2 FRNs were dated 1976 and have green seals. If you have a US Note, there's more information at the question "What is the value of a 1928 US 2 dollar bill?"
Please check your bill again. There were no 1926 US bills; the date is most likely 1928.If so, there's more information the at question "What is the value of a 1928 G US 2 dollar bill?".
"F" is the highest series letter for 1928 $5 red-seal notes. Please check your bill again and see the question "What is the value of a 1928 US 5 dollar bill with a red seal?" for more information.
The green seal indicates that your bill is a Federal Reserve Note. All 1928 B $20 bills were printed as FRNs. Please see the question "What is the value of a 1928 B US 20 dollar bill?" for more information.
1928 $50 bills weren't issued as silver certificates. Please check the wording across your bill's top front; then see one of the following questions:"What is the value of a 1928 US 50 dollar Federal Reserve Note?""What is the value of a 1928 US 50 dollar gold certificate?"
The green seal indicates that your bill is a Federal Reserve Note. Please see "What is the value of a 1928 D US 5 dollar Federal Reserve note?" for more information.
Please check the bill's date - it should be 1928, and its type - it should be a United States Note.There's more information at the question "What is the value of a 1928 C US 2 dollar bill?".
the serial number does not match the series
There were no $2 bills dated 1929. However, letters for the 1928 series go up to G so if that's what you have, please see the question "What is the value of a 1928 G US 2 dollar bill?"
Please check again and post a new question. No $2 bills are dated 1929.If your bill's date is 1928, there's more information at the question "What is the value of a 1928 [letter] US 2 dollar bill?"
Please check your bill again and post a new, separate question. "G" is the highest series letter for 1928 US $2 bills.
Your bill is called a United States Note rather than a promissory note. There were eight different subseries within the 1928 series date; please see the question "What is the value of a 1928 US 2 dollar bill?" for specific information about values.
All 1928 $2 bills were printed with red seals, so it's possible your bill has changed color due to age or chemical exposure. Please see the question "What is the value of a 1928 D US 2 dollar bill?" for more information.