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?"
A denomination is needed. Please look for questions in the form "What is the value of a 1928 A US [denomination] dollar Federal Reserve Note?" for specific information.
"A" is the highest series letter for 1928 $50 Federal Reserve Notes. You may be looking at the Federal Reserve District letter instead - please see the question "What is the value of a 1928 US 50 dollar Federal Reserve Note?" for more information.
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.
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.
All 1928 $20 Federal Reserve Notes carried the phrase "Redeemable in Gold", although they weren't gold certificates. There were also gold certificates with that denomination but they have gold seals and lack the words Federal Reserve Note. Please see the question "What is the value of a 1928 US 20 dollar Federal Reserve Note?" for more information.
"A" is the highest series letter for 1928 $50 Federal Reserve Notes. "K" is most likely the Federal Reserve District letter. The series letter, if any, on US bills is next to the date. Please see the question "What is the value of a 1928 US 50 dollar Federal Reserve Note?" for more information on values.
1928 $50 bills were issued as gold certificates and as Federal Reserve Notes but they're not the same. Please check the wording across your bill's top front as well as its seal color*; 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?"* Gold certificates have gold seals and FRNs have green seals.
Not every old bill is automatically a certificate so it's important to check carefully. If it has a gold seal and says "Gold Certificate", see the question "What is the value of a 1928 US 10 dollar gold certificate?" for values. If it has a green seal and says "Federal Reserve Note", it's not a certificate, it's a Federal Reserve Note. See the question "What is the value of a 1928 US 10 dollar Federal Reserve Note?" for values.
1928-series $100 bills weren't issued as silver certificates, only gold certificates and Federal Reserve Notes. Please look at the bill's front to determine which you have; then check one of the following: "What is the value of a 1928 US 100 dollar Federal Reserve Note?" "What is the value of a 1928 US 100 dollar gold certificate?"
That phrase appeared on all Federal Reserve Notes of the time because the US still issued gold-backed currency, even though FRNs were not gold certificates. Please see the question "What is the value of a 1928 US 5 dollar Federal Reserve Note?" for more information.
All 1928 $5 Federal Reserve Notes carried the phrase "Redeemable in Gold", although they weren't gold certificates and in fact no gold certificates with that denomination were printed. Please see the question "What is the value of a 1928 A US 5 dollar Federal Reserve Note?" for more information.
Regardless of the Federal Reserve District that distributed the bill, as of 09/2012 a 1928 $100 FRN retails for $125 to $180 depending on condition.
The value of a 1928 twenty dollar bill that says "The Federal Reserve Missouri Bank of St. Louis" would actually depend on a number of things. The main factor that should be considered when determining value would be the condition of the bill.
Your bill is actually called a Federal Reserve Note, like modern $20 bills, rather than "a bank note of Chicago". Chicago is simply the Federal Reserve District location that distributed the bill. Please see the question "What is the value of a 1928 US 20 dollar Federal Reserve Note?" for more information.
Please don't assume that every old bill has to be a silver certificate. 1928 $10 bills were issued as gold certificates with gold seals and as Federal Reserve Notes, with the familiar green seal and the words "Federal Reserve Note" across the top.Please check the bill's seal color and wording across your bill's top front; then see one of the following questions:"What is the value of a 1928 US 10 dollar Federal Reserve Note?""What is the value of a 1928 US 10 dollar gold certificate?"
If very worn, about $15. Moderate wear, about $30
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?"
All 1928 $5 Federal Reserve Notes carried the phrase "Redeemable in Gold", but they weren't gold certificates and in fact no gold certificates with that denomination were printed. In addition, the bill was distributed by the Federal Reserve Bank located in Cleveland; it wasn't produced by a bank called the Bank of Cleveland. Please see the question "What is the value of a 1928 US 5 dollar Federal Reserve Note?" for more information.
The first $2 Federal Reserve Notes were issued in 1976. The banner across its top and the red seal indicate it's a United States Note, a form of paper money issued directly by the federal government until the late 1960s. Please see the question "What is the value of a 1928 D US 2 dollar bill?" for more information.
Green seals are used on all Federal Reserve Notes dated 1928 to the present.
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.
All 1928 $100 FRNs carried the wording that they were redeemable in gold. There's more information at the Related Question.
It's actually called the Federal Reserve Bank of Chicago. However all 1928 Federal Reserve Notes had green seals, so please check your bill again and post a new, separate question.
Please don't assume that every old bill is a silver certificate. The banner across its top and the green seal indicate it's a Federal Reserve Note, the same type of paper money used today. There's more information at the question "What is the value of a 1928 B US 10 dollar Federal Reserve Note".
Please don't assume that every bill is a Federal Reserve Note. The banner across its top and the red seal indicate it's a United States Note, a form of paper money issued directly by the Federal government. US Notes were discontinued in the 1960s. There's more information at the question "What is the value of a 1928 G US 2 dollar bill?".