What are 1905 two and half dollar gold coins worth?
In circulated condition, they're worth $150-$175
Most uncirculated ones are worth $200-$400
A real nice uncirculated one is worth over $1,000 but you need to have it professionally graded.
As of 10/2010, the gold content of this coin is worth about $170.
Like all other current dollar coins it's just gold-COLOR, not real gold. After all, even the most boneheaded government functionary wouldn't authorize a coin that would be worth 300 or 400 bucks and put it in circulation for a dollar.... which is exactly what all current dollar coins are worth, $1. One dollar.
Four new gold dollars and the words In God We Trust are upside down on one of them how much is it worth?
A "gold" 1979 Susan B Anthony dollar would be a regular dollar coated in gold (or gold paint). Numismatically, it's worth about a dollar. If it is coated with real gold AND it is a thick enough to be worth anything AND you could get the gold off, it might be worth a bit more (especially if you could salvage the coin itself for a dollar). Broadly speaking, "collectable coins", such as this, aren't.
The gold colored Sacajawea dollars are worth a dollar. All current U.S. $1 coins are not gold, they're gold-colored. The metal is a manganese-brass alloy. They're worth $1 each, regardless of the design. Feel free to spend them as billions have been struck. OTOH $1 gold coins issued in the 1800s were real gold and are worth considerably more than $1, but you need to know their dates and mint marks.