LOL, just now seeing this thread.
Thats awesome because that necklace is probably worth more than the machine it was in.
Coin looks perfectly fine to me.
Yes, its in a gaudy as hell mount, but people did that back in the day when gold was cheap (think 1980s Mr. T).
This is pretty typical of the 1960s and 1970s.
Value on the coin depends what it looks like out of the bezel and if the bezel actually left mount marks (prong marks) on the coin.
Current spot price on gold is around $1785 per ounce and melt value alone on the coin is around $1722.
Jewelry grade bid on messed up $20s is around $1770 (for worst possible condition), sell price is $1870 (about $100 spread buy and sell).
XF bid is around $1795 with a sell of $1895
Generic UNC (raw uncertified) is $1830 bid with ask of $1930.
The question really is if the coin will have evidence of mounting or being in jewelry if you remove it from the bezel.
Could be worth over 2k, but I would bet its more of the generic price around $1800-$1900 range.
Now, depending on what the weight of the bezel and the chain you have quite a chunk of change just in that.
Its marked 750, which is 18 Karat gold (75% gold) and that's a pretty big chain and mount.
So whatever the bezel and chain weigh, throw it on a scale and divide that by 31.1gms (troy once) and multiply it by 0.75 and that will give you the aggregate gold weight of the chain and bezel.