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.
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.
All 1928 $100 FRNs carried the wording that they were redeemable in gold. There's more information at the Related Question.
There aren't any U.S. government $5 gold certificates. It's possible you have something issued by a private bank. Please post a new question with a more complete description.
On the 5 dollar bill: Redeemable in gold on demand at the united states treasury or in gold or lawful money at any federal reserve bank. 1928 series A A.W. Mellon secretary of the treasury
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.
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.
All 1928 $100 FRNs carried the wording that they were redeemable in gold. There's more information at the Related Question.
A 1928 $50 bill that is redeemable in gold on demand is known as a Gold Certificate. These certificates were issued during a time when the US dollar was backed by gold. As a collectible item, the value of the bill would depend on factors such as its condition and rarity. They can be worth more than their face value to collectors and currency enthusiasts.
There aren't any U.S. government $5 gold certificates. It's possible you have something issued by a private bank. Please post a new question with a more complete description.
Gold certificates were issued for gold, while silver certificates were issued for silver. They were separate types of bills with separate names redeemable for separate types of precious metal.
Black Gold - 1928 is rated/received certificates of: USA:Passed (National Board of Review)
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.
On the 5 dollar bill: Redeemable in gold on demand at the united states treasury or in gold or lawful money at any federal reserve bank. 1928 series A A.W. Mellon secretary of the treasury
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.
Even though your bills have the phrase "redeemable in gold" on them they're Federal Reserve Notes rather than gold notes. $10 gold certificates were also printed in the 1928 series but they don't have any series letters. 1928 A $10 FRNs are definitely worth more than 1928 B bills, but the difference depends on the issuing Federal Reserve Bank letter. Please see the questions "What is the value of a 1928 A US 10 dollar bill?" and " ... 1928 B ... " for more information.
There were no 1928A gold certificates printed, only 1928 with no series letter. (Series letters, when present, are next to the date, not beside the serial number or elsewhere.) If you have a plain 1928 bill, its value would range from $250 in worn condition to about $750 if it's only slightly worn.