Blued (oil blackened) versus Parkerized

[Surpmil]

I have a 1913 Mk.III that was refurbished at RSAF(E) in 1931. The cocking piece, trigger, safety and spring and cutoff are all oil-blacked in contrast to the fine rust-blue on the body, bolt etc. My recollection was that the blacked parts were dipped in a sort of lacquer or shellac to preserve their finish somewhat. In original condition they show a certain sheen which I don't believe a plain oil blacked surface would exhibit unless highly polished.

Modern hot-tank bluing does not add any sort of layer to the surface, unlike rust bluing or parkerizing. Parkerizing is a "friable" coating which wears away as required and is or was much used in engine rebuilding to hold oil during the first moments of running in.