So far, I have not found any relevant information about the Palermo Court Prison. Concluding from the stationery below, this prison also served as a transit point before being transferred to Ustica concentration camp...
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Stationery, written in Palermo Court Prison (15.III.42), censored by prison censor (17.MAR.42) and sent through Palermo Ferrovia (18.III.42) to Split. From the message: "... I am in the transit for the Ustica concentration camp ...".