During the Imperial era nickel plating became a popular way to cover up a multitude of sins with blades that were not perfectly polished. That was carried on into the Third Reich era for swords and some daggers.

The ‘cross grained’ variety of political blades replaced the earlier fully polished blades as a cost cutting measure. Many had mottos that were intentionally darkened by bluing the mottos after etching. Nickel plating would have obliterated the blued/darkened mottos. And for the ones that were only etched, nickel plating would have tended to coverup the mottos to some extent. Especially if the plating depth was not carefully controlled. And trying to acid etch over/on top of nickel plating has its own set of problems. Which are all reasons why I have not personally seen a blade that I thought was period plated.

As for the non political blades some makers plated while some did not. With time also being a factor as nickel began to be conserved for the war effort. With polished steel blades becoming more common as manufacturing standards deteriorated from a materials standpoint. FP