I had wanted to have one of these big coins since I was a kid in 1964 when I saw one in R. S. Yeoman's book A Catalog of Modern World Coins
I finally got one after 60 years.
Belgian Congo 50 Francs 1944
Silver, 35 mm, 17.37 gm, 500 fine
Obverse: Elephant facing left / 1944
Reverse: BANQUE DU CONGO BELGE (French) / BANK VAN BELGISCH CONGO (Flemish) / 50 FR
Mint: South African Mint in Pretoria
It was later joined by a similar but smaller coin:
Belgian Congo 2 Francs 1943
Brass, 28x25 mm, 5.93 gm, hexagonal
Mint: Philadelphia Mint
The United States was happy to mint these coins for the Belgian authorities.
The Belgian Congo had a large uranium mine which had been closed in 1937 as no one wanted uranium.
The mine was re-opened in 1944 and the newly mined uranium was sent to America.