Hello. I can assist you with your question.
To answer your question, they can be valuable, depending on several factors.
Do you have a picture of the bill?
On ebay, be VERY careful and make sure that it is not a "copy"
That it has the gold seal indicates that it's a Gold Certificate, as you said, and not a federal reserve not redeemable in gold.
There is a 1928 series of each
One in Very Good condition is worth about $210
Very Fine condition about $280
I am very careful on "copies" and ebay's buyer protection gives great coverage. I do not have a picture of the bill. How much (ballpark est) is the thing worth. This guy is selling it for $97 but I am looking at others going for 2-5X that much. Sometimes I luck into sellers who sell cheap and this guy runs a coin/money business with a 100% feedback score, meaning what he sells is good and as described.
Second question: I am also looking at some bills that say "redeemable in gold". $10 paper notes. What are they? As I said I am a "coin" collector, not paper money, so I am trying to get educated on them. ---Deb
Those are called Federal Reserve Notes
Both Gold Certificates and Federal Reserve Notes were issued.
Thanks, XXXXX XXXXX are they worth?
A $10 Federal reserve note, 1928 series is worth about $70 in Very Good/Fine
And as I siad for the $20 Gold Certificate