The lens I have available might be too convex. Here is a photo.

It is 7-7/8" diameter and is about 2" tall at the highest point. The outside is smooth, flutes do extend out to the side.
The numbers on the lens are as follows.
12 o'clock - 2B89 M2
5:30 - 507686
6:30 - No. XD 7148