Appears to be EN, electroless nickel. Probably very thin. EN is not a good barrier finish and not sacrificial at all.
EN can be applied in a very controlled way, .0001 - .0002 is easily achieved. One way to tell if EN vs. Nickel Chrome or electrolytic Nickel, look into a crevice, if plated it is EN. EN covers everthing equally (no electricity) unless masked by paint or tape. Electrolytic Nickel travels in straight lines, cannot turn corners, a hole or crevice will be bare. EN is duller especially the hard versions. All nickel has a yellow tinge, turns blue when chromed.
I have a 1911 I had EN plated, hard Rc60 then baked to harden further and reduce chance of hydrogen embrittlement. You can not scratch it! Has a much deeper and strong finish that this one based on picture. Had to use carbide reamers to clean out the holes. Not any issue on rails and such, only added about .0003.
A good hard chrome/plating shop would be able to tell you what it is.
A little history, years ago most if not all nickel plating was preceded by copper. The copper was polished and the nickel applied. Copper was used to promote the nickel sticking (nickel does not like steel) and to allow easy polish/buff to remove defects in the base steel. The nickel plating then came out of tank very dull and almost white. You had to then polish it to get the bright reflective finish. After this, if you wanted to make it "chrome plated" you put it back through another system and applied chrome, .00001-2 thick. You can always tell chrome from NI, NI has a yellow tinge, the same part when chromed has a brighter "bluer" look.
To reduce cost, the copper was eliminated on cheaper items. Still had to polish to get a bright finish. Now days the bath has brighteners to keep the finish nice and clean. It does, however, show up every defect in the base material.
Even a stainless steel part will look better and be "bluer" if chrome plated. Also passivates the surface. SS hub caps are still chrome plated to reduce rust and make them hold up in winter salt conditions.