No US $100.00 gold coins were ever made, so a value is not available.
To determine the exact value of a 1928 US dollar coin, a couple different factors would need to be taken into consideration. Most important factor being, the condition of the coin.
The first Australian Two Hundred Dollar coins were issued in 1980.
It should be valued at $15 - $30 depending on the condition of the coin.
Circulated coins are $25.00-$90.00 Mint State examples are $150.00 or more
If you mean a 1928 Peace dollar with No mint mark It's the key date to the series the value in VF-20 is $475.00. I suggest you take it to a coin dealer, because I have seen many 1928 S mint coins with the mint mark removed.
Please turn the coin over and check the denomination on the back. You'll find it's a HALF dollar.
Your 1928 eagle silver dollar is actually a 1928 PEACE dollar, the first Silver Eagle bullion coin was made in 1986. But for this year of issue Peace dollar it's very important to see if there is a mintmark (S) on the reverse just above the eagles tail it makes a big difference in value. If you see the S a low value for the coin is $16.00 no S low value is $250.00. Take it to a dealer or collector for an assessment
No gold coins were struck in 1928, please look at the date again. 1929 was the only year the coins were struck.
A "one dollar" coin has the value of one dollar!
The National Motto E PLURIBUS UNUM is on all Peace dollars and does not add to the value of the coin. What does add to the value is if it has a mintmark or not and the condition of the coin. In circulated condition a 1928 Peace dollar with out a mintmark (only a "S") is valued at $293.00-$456.00 with out the mintmark value is $17.00-$89.00
SIMPLE ANSWER: The 1928 Philadelphia issue (no mintmark) coin. Average retail value is $275.00 for a coin graded G-4.
The Denver mint did not strike any silver dollars in 1928. You may have a 1928-S where the S is indistinct. This coin is worth $20 to $30 depending on condition.