Franz Kafka – the workers' friend (2018)

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?

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