Hi Nemrod
The round crown on the right is the original Royal Aqua Master.
The square one the left is from an early Conshelf (or maybe a very late RAM).
The one from Treasureman is from a modern Conshelf. The only difference is the silver looking plating.
All the crowns (spring blocks) are closed at the top to form the LP balancing chamber to make it a balanced first stage. They are all interchangeable.
My first impression on the pictures from Treasureman is that those groves you see were accidentally filed too deeply. Some times when using a Conshelf spring block it is good to lightly round that edge. Again this is a total preliminary speculation from looking at that picture and it is far from been conclusive.
It is hard for me to see details about your little white washer, but it looks like it could be the O-ring back up ring that goes inside the RAM (Conshelf) spring block / LP chamber. The O-ring back up ring inside that chamber is very important. It helps keep the O-ring from extruding into the chamber.
The back up ring goes in first and then the O-ring. The O-ring is being push into the LP chamber by the tank pressure. Back-up rings are commonly used for high pressure O-ring service. It is particularly important for higher pressures (3000 psi or higher).
I have seen at least three different back up rings used by USD: 1) a white split one in the earlier regulators, 2) a white solid ring similar to the one you are showing, 3) and a black ring with a slight grove facing the O-ring.
Here is what a DA Aqua Master spring block looks like. It is open at the top since it is not forming a low pressure chamber. It is just a spring guide.
This picture is from Bryan’s store:
