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Excalibolg is a kanabō, a real (albeit archaic) weapon, though with both exaggerated size and spikes rather than studs. It does, however, have the grip of a baseball bat - even the tape!
Additionally, its name may be derived from Excalibur and Caladbolg (a somewhat less well known sword from Irish legend).
Sakura-kun's school is "St. Guernica's Academy" - there is no "Saint Guernica", however "Guernica" is the name of the famous painting by Pablo Picasso symbolizing the bombing of Guernica during the Spanish Civil War. "Guernica shows suffering people, animals, and buildings wrenched by violence and chaos."