It happens whey you try to answer too quickly, while being stuffed with medication
The marking was done, according to German sources (including Kornmayer), for a US dealer by a German gunsmith, in order to have a laugh at the expense of US collectors and boost the prices of pistols that were, by the standards of the day, barely collectible otherwise.
But I think enough has been said about it. We seem to keep going around in circles anyway.
At least the Germans find it amusing