At first I wondered if it may be the 42M, but that tank has a 40mm cannon which this is clearly not in the picture. At any rate, it's not a "heavy tank".
Here's one of the 39M while I'm at it.
Later Toldis (1942 and later) were upgunned to a 40mm.
It’s hard to get a scale for how small it was without people in the picture. It brought to mind the Czech tankettes. http://en.wikipedia.org/wiki/AH-IV