Try the old finger nail trick, press your finer nail end on the surface and with varying pressure drag it from good metal[shiny] to dull, you may feel a definitive drop off over the edge, or a raised edge on the icky part?
If you feel a drop the plating is missing [corroded away] which is what it looks like to me? If you take off the ick with your finger nail all well and good.
I've looked at my razor same model as this and my mind lends toward chrome? yet i cant really say 100% or are they nickel, dipped it in the plating tank, it went ugly which lends toward chrome?
Polish? Lemon juice? Citric acid? you may have? Any thing you try shows brass, well it is brass underneath. The top picture is showing a brass-ish dull colour on the very top right?
I, myself, get really rude and upfront with this type of ick, hydrochloric, phosphoric, oxalic acids or lye and chlorine, not wrecked one yet, but that does not mean that it can't happen. It's a case by case decision, or if mild does not work, we progress to wild. And I'm impatient !!