The Washington Mint is a private company NOT associated with the actual U.S. Mint. Any silver coin they produce is worth its bullion value only.
If you mean a 1990 Silver Eagle only Proof and bullion coins were struck in that year. From 1986 to 1992, proof Silver Eagle coins were minted at San Francisco and these coins bear the "S" mintmark and have a current retail value of $20.00. Bullion Silver Eagle coins dated 1990 were also struck at San Francisco but do not have mintmarks, the value of these coins depends on the spot price of silver at time of sale. As of today it's about $17.50.
FG stands for Frank Gasparro, the coin's designer. I assume you have a small dollar coin with a picture of Susan B. Anthony on the front and an image of the Apollo Mission eagle on the back. This was a standard-issue coin at the time and is worth only face value, unless it's a Proof coin in its original holder.
What forms did the lender require?
You generally can't buy silver dollars or any older silver coins at a bank. Because the value of the coin greatly exceeds the face value of the coin, if someone wanted to deposit a silver dollar they would only give them $1 for it, when the coin is worth at least $30 in silver content. Because of this few people ever deposit silver coins and the ones that are deposited are bought by the bank employees as curiosities. The only "silver" dollars you might find at a bank are Eisenhower dollars, but these contain no silver and are sold for $1, but since many people keep them as curiosities, there are few banks that carry them in stock, but at some banks you might find a few. Some banks do sell silver proof sets and other collector coins, but the prices that they sell it for is much more than it would cost you to go to a coin shop and buy the exact same set for.
You just spend it. Unless you have a coin in a mint-set with an "S" mintmark that is either proof or uncirculated, your coin is worth $1.
It depends greatly on the year, early silver dollar proof dollars can be worth several thousand dollars, modern silver dollar proofs of common dates might be worth $20 or so for silver scrap.
The value of a 1984 Canadian proof dollar is about $12.
A 40% silver "S" mintmark proof Eisenhower contains .3161oz of pure silver or 8.96128 grams
One dollar...
The silver proof 1997-S Kennedy half dollar has an current average value of $15.50.
About $24
the 3 coin proof set with 2 silver proof one dollar coins and one 10 dollar proof gold coin is worth about $550.00 retail the 3 coin proof set with 2 silver proof one dollar coins and one 10 dollar proof gold coin is worth about $550.00 retail
Value for a proof 1962 is $10.00-$12.00
Unless it is a "proof" coin (actual silver), it is worth one dollar.
The 1988-S proof Seoul Olympics silver dollar has a current retail value of $15.00
Most New Zealand silver Proof coins are sterling silver containing 92.5% silver.
$50-$65