Could you help me identify these vintage bricks with holes in the studs?
LEGO made plastic bricks from 1949 and didn't get the patent for the tubes underneath until 1958, in the years between they made plenty of bricks with nothing underneath.

Many (I don't remember if it's all) of the (larger) LEGO bricks from that era, has a slot in one side.

That being said, with the small holes through the studs on the 2x4 and the slightly recessed studs, these bricks doesn't look like anything I've ever seen from LEGO.

Square holes underneath I have seen though, so that's not an argument against your green plate being LEGO, but without having seen it, I can't say for sure.