The assy manual doesn't appear to call out the center link idler arm pin/bolt finish, as it is part of the 3304 assy.
Only hardware items, screws, bolts, washers and nuts, had a finish code (blank was unfinished, which is still a code).
I thought it might be heat treated as the rest of the center link was heat treated.
Heat treated or not?
Those items were hot stamped from rod. At the end of the process, they were dropped into an oil bath, not a real heat treatment, but more to cool the part for handling and give some rust protection.
I haven't yet cleaned up the machined areas where the tie rod and ram go through. I assume all of them have the shiny, machined surface (as well under the pin).
I don't believe any machining was involved other than drilling the mounting holes and the threading of the other end.
So, what do
you do?
I don't know, but I would do a light phosphate and oil treatment, primarily to give some surface protection.
RUST IS YOU ENEMY.
Jim (USN trained)