I sorted through old 3D printed parts today, deciding what to keep and what to discard. I was able to do some archaeology on several generations of relays:

Early designs (bottom right) were based on snap-together frames so that different ideas could be tried and and altered quickly. This proved too flimsy and these relays typically failed mechanically after a few hundred operations unless glued together. Some designs (top right, top left and bottom left) were one-offs and not good enough to displace already successful designs (but with further work they might be viable). Successful designs tend to lead to multiple versions with variations in the structures that give the relay its characteristics.