How many sonic screwdrivers have there been

There's the one which Jon Pertwee through God knows which doctor used-- it's one that's silver, with a red head. Then there's the one that the ninth and tenth doctors used, which got broken by Tennant in Martha's first episode. He then got a new one which looked just like the first. Then that one was broken by Matt Smith in Amy's first episode, and replaced by on which lit up green. Finally, that one broke in the special which just came out. So let me see...

Probably more than five.