The type of cross that has three horizontal bars is usually called a Russian Cross. This one was carved in black walnut a long time ago, so I don’t have precise measurements, but I do seem to remember that it was about 35 cm tall (13.5 inches). It's waxed only; that is the natural color of black walnut.

In case you don't know why there's a skull underneath the cross in Eastern Orthodox representations of the Crucifixion here's the explanation: in the Bible's description of the event it is said that Christ was Crucified at a place known as "Golgotha" which means "skull" in Arameic. The widely spread tradition in the east is that that was the place where the first man, Adam, was burried and, thus, the skull you see is his. So what you're looking at is not just a visual representation of a specific moment in time (the crucifixion) but actuallly a much longer period of human history condensed in one scene - Jesus Christ redeeming mankind (Adam).