Does anyone know what these are?

So I have these weird Lego bricks, some of which have letters and or numbers on the duds. They are pretty uncommon colours too. Like weirdly skin toned. Some of them have the official lego mark on them, some don’t. But they all fit perfectly together with each other and with other newer official bricks too. They are obviously old. I tried searching for similar ones but all I get is results for braille bricks or newer pieces with letters painted on the sides etc. I’m curious if anyone knows...