More details are needed - specifically, what denomination? "Bundesrepublik Deutschland" means "Federal Republic of Germany", so your question is similar to saying "What is a 1975 United States worth?".
In any case, most German coins from that period are only worth face value or a bit more. At the time Germany switched to the euro in 2002 the mark was worth about 50 cents and the pfennig was worth about 1/2 cent, so that may help to pin down your coin's value.
About 25 Euro Cent
£3000
$28,000 today is the same as $4,514.50 in 1970.
No US dollar coin is dated 1975, look at the coin again and post new question.
1¢. At the time it was replaced by the euro (2002) the Deutschmark was worth about 50¢ U.S.
About 25 Euro Cent
How much is my 1975 Cincinnati reds world championship LP worth
Money
A 1975 US What? post new question.
a lot
$400
£3000
The coin is still in circulation today and is only face value
Unless it's uncirculated, about 30¢ (face value)
Take it to a collector
$2.40
Face value only