Where is this knock-off LEGO brick from? These are some of the non-LEGO pieces I had in my LEGO collection when I was a child, and I was told they were old LEGO, but any site on the history of LEGO completely failed to show anything like this, so they have to be knock-offs.  

  

They are likely made in the 60's but it could be earlier. It's compatible with LEGO, except that the studs are higher, so you can't put a thin brick on top of them. The plastic is softer and just slightly translucent. I like their solution for the underside, very neat, and a clever attempt to pass by the LEGO design patents. I don't know the manufacturer, and would appreciate any information.
As others have pointed out, these are Montini building blocks.


Montini building blocks were produced by Berco Lux in Tiel, The Netherlands between 1960-1969. The plastic is much softer and the colors are a little different.
In 1969 production was stopped because of the Lego patent.
Montini history and the conflict with Lego ( in Dutch)