Orwell spoke of this obvious truth many times, essentially that history is written by the victors or winners... he is not alone, many before him noticed this fact (long before Braveheart came to the television screen). History deals in facts to a degree, when it speaks of casualty figures, dates and statistics of battles (the leaders, scale and scope perhaps, - though influences and impact are opinions/guessing); nothing is wrong acknowledging that history is distorted by the authors prejudices and perspective, sometimes the best authors are the ones that do acknowledge this fact (like John Kenneth Galbraith in his biography, his obvious prejudices he readily acknowledged, but because he managed the war economy for the US and supervised many of the post war economic studies, including interviewing Speer and others, his book is valuable), the worse are those that insufferably preach their objectivity and speak as though their arguments are facts. What I have noticed generally, is that the best authors, those most capable of objectivity, are English authors, almost alone can find the strength to be critical of their own countries responsibility in both world wars, - Germans perhaps the most insufferable in the fact the wallow in the guilt they have been bathed (drown) in (indoctrinated) since 1945. Most are social democrats or former communists, at least the ones that found their way into English translations...
Anyway, there is no innocent nation in the two world wars, naturally none of are responsible for our fathers and grandfathers roles, most of whom are innocent as well, as politicians and bankers are the only beneficiaries of wars...
As to the transition to numeric acceptance, Bryan/Görtz might have something on this, or Görtz anyway, but probably between 1922-1923, an insane period up to that point. By 1924 we know numeric acceptance came to the forefront, Simson's production all carry numeric acceptance, though still have some evidence of the transition. DWM seemingly uses the more formal waffenamts quite early (e/29), probably about the sametime.
I suspect very little small arms production occurred at the factories after 1919 or Versailles (June 1919), but is a fact that factories hid illegal weapons rather than surrender them voluntarily (without compensation, Mauser was caught a couple times with illegal weapons). Likely much of this material was made at the end or shortly after the war ended. Things were pretty nuts at the end of the war in Germany, indeed all of Central Europe, - we also know that Danzig continued making weapons for the Poles long after the war. All the arsenals did similar trying to keep work forces employed, though generally transitioning to commercial arms made from military components (also consumer products their facility could fabricate). Little of this was militarist in purpose, though the communists in Bavaria probably sought arms from Amberg for there purposes, most of it was to find some employment for their workers to feed their families.