You need to be much more specific. There are several South African Coins dated 1966 ranging in value from less than a penny to several hundred dollars. Post a new question including the denomination and an estimate of the coin's condition.
The 1966 South African 50 cents coin is between $3.00 and $6.00.
It is 80% silver and worth about silver melt, about $9 at the time of writing. 1966 is the most common year for the 1 Rand coin of that series with about 1.5 million minted.
South African Border War happened in 1966.
$10,000 US Dollars in 1966 would be worth $66,328 in today's money.
The 1966 Kennedy half dollar is 40% silver and worth about $5.00.
I won't seal 1966 coins 50c praise
Hendrik Frensch Verwoerd
yes 3480
£1,000
R20 000
Just about what is was worth in 1966, more than likely, without any adjustment for inflation.
20 million