OK- - - -on closer examination, I see the pry bar slot at about the 11:00 position on your first picture. The white-painted bead ring will have a couple of relieved areas that will allow the ring to be pried upwards and slid sideways off the main part of the wheel once the tire is deflated and pushed or hammered away from the bead rings. That outer ring does not have a split anywhere, nor does the wheel. That type of 2-piece wheel is very uncommon with 20" tires. The 18" wheels used on my 1959 1-ton flatbed had that style of lock ring. The locking lip on that type of wheel is VERY shallow, and it's susceptible to rust and/or damage while removing/installing the tires.
Jerry
