Alrighty then...
I removed the stock from my M2T to determine this... so you owe me a bottle of Bombay Sapphire.
The shim is .059" thick all the way around and marked 'B'. No cast, and according to the chart, a 60mm offset. The plate in the rear that goes under the nut is marked 'B-SX/A-DX" on on side and 'B-DX/A-SX" on the other side. The hole in the plate is offset in two directions from center.
These parts come from what Benelli calls a "drop change kit". If you go to page 84 in the manual, what I'm using corresponds to drop change schedule 'B'.
I have several other shims marked 'A, C, D and Z' and a plate marked 'C-DX/Z-SX' on one side and 'C-SX/Z-DX' on the other.
What do I know about all this stuff? Not much... I am far away from a drop/cast shim expert.
Even though I'm left handed, I didn't want any cast, so I just tossed shims in until I found one that when shouldered, brought the sights right to my eye with no cheek weld adjustments.
Recommendation... get the whole drop change kit from Benelli, or who ever you can find that will sell you one... Brownells, Midway, some dude on the forums, and you can fit it to your requirements.
Cheers,
C