Prewar Schwinn chain adjuster bolts: What finish?

[bloo]

What finish did Prewar Schwinn chain adjusters have originally? I just repaired one of mine that had a broken tip. I drilled a hole in it on the lathe, and silver soldered a bit of steel rod in. They have been covered in silver paint since the 70s, but are bare now.

Cad plated? Zinc? Black oxide? Bare?

Photo of repaired bolt (left

 

[Obi-Wan Schwinnobi]

Cad if I remember correctly. Think I’ve seen some blackout ones too but maybe not