1939 50 Centimes Francaise Coin

Hello All 👋 

I was curious if anyone knows why some of these coins are nickel and some are Copper-aluminium if they are the same year?

Thanks!

And they are Patterns, many pattern coins would be tried out using different materials before they decided which one to use for minting.

An essai  or pattern, is a kind of proof issue. Only a small number were struck. There were no nickel ones put into circulation.

Someone has worked hard in the Numista catalog to add all the essai as separate pages. They are interesting academicly, but it's just confusing and distracting for an ordinary collector.