It is raining again here in Oregon so I got after another project inspecting sheaves and connecting pins on the mast. The main halyard was fine with the exception that the pin being used didn't match the sheave, so I drilled for the larger 5/16" pin and installed it. Then I went to the sheave box and as much as anything else I was curious if there was going to be corrosion from contact between the box and the mast and was happy to see that wasn't a problem. Then I noticed that the small sheave at the back was was wallowing out its holes and the pin was fused in the sheave. Reading this thread it isn't clear to me if the pins are supposed to be a friction fit with the sheave and the pins rotate in the housing, or if they are supposed to be fixed in place by the peening of the pin ends and the sheaves rotate on the pin. Since this hole is now wallowed out peening a new pin would not be effective anymore.
This sheave is spinning freely and likely not going to cause a problem in its current condition, but if there is an easy fix now would be the time to do it.