Deep, I think the elevation was fixed by friction only, have never seen anything else used on those. The barrel should not move during time projectile is moving out of bore since all forces act through center pivot at rear, and since friction there would increase greatly during recoil. There might be some movement after projectile is gone due to muzzle blast or whatever, but that would not bother accuracy.
The Manby here now is in essentially new condition, without iron base, only marks are a large "13" on top of barrel. We shot the ball out of that somewhat rustier one you may have seen photos of; I kept the ball, which was apparently an original Manby ball with recess and bar to tie line onto it, the only such ball I've seen. I have many photos of it somewhere on this 'puter.
