There's a typo in the first paragraph... Die Arbeiter-Unfall-Versicherungs-Anhalt - should be "Anstalt". A followup of this institution has survived in Austria to this day. The "Allgemeine Unfallversicherungsanstalt", still abbreviated AUVA. They have regular advertisement spots on public television too

Can anyone point to any sources on these anonymous letters?

I'm pretty sure they are from this collection:

https://en.wikipedia.org/wiki/Franz_Kafka:_The_Office_Writin...

(Also I believe these letters are 'anonymous' not in the sense that their authorship is unknown, but in that they were published under the institutional name of the Insurance Institute where he was employed, not under his personal name.)

perhaps old models of insurance through quasi-governmental institutes should be reconsidered as a replacement for what we have today