I quote fromhttp://www.literarytraveler.com/literary_articles/franz_kafka_prague.aspx
"On the east side of Maiselova, north of Siroka (where sits the Franz Kafka Cafe, a pub that merely appropriates his name), is the pink Jewish Town Hall, the civic hub for Prague's Jews since the baroque era. The tower of this building contains the famous Hebrew clock whose hands turn backward."
Better to use one of those which has a confirmed pre WWI pedigree? There is a Kafka Connection with the Hotel Europa Cafe
"On the second floor of the Café [Grand Hotel Europa] in December 1912, Kafka read his newly composed "The Judgment" to an appreciative audience"