2"mortar Mk2 lensatic sight.

[Topfmine]

So how rare is the 2" mortar with the heavy base plate, all I have seen is the small base plate that looks like a short bit of angle iron. I thought this lensatic sight was discontinued when they changed to the spade plate design around about 1942-43. Then we just used a painted like on the tube. Are we talking about the same 2"mortar.