Ha ha I was starting to suspect that due to your hints, and was already thinking myself "amazing idea from Reaper7"
Anyway ...
I think you can actually clone the dial and give it a duplicated identity as long as you rename it, since we can clone the TDC dials with no problems
BUT
there is an alternative solution to what you want to do
, which might work well meanwhile:
Simply, do your background and put along the top of it the bearing dial, all in one single graphic, then make all the scope screen background transparent at the sides AND at the bearing dial position of the scope. Both background and vernier will rotate together, though since you will only see the background (Lower 95% or so of the screen) and the vernier in the periscope, the effect will be achieved
Magnific idea Reaper, I really love this alternative thinking, kudos to you