Item: Single tuning fork, stamped “s.b.l.” and “C1 Tony. C. Bol. Pa.”. Function: A two-pronged acoustic resonator that rings at a specific pitch when struck — used for instrument tuning, medical auditory tests and sound therapy. Condition: Good vintage condition — surface wear consistent with age and use. The fork rings cleanly when struck; no cracks or visible repairs. See photos for details. Markings: s.b.l. (maker/distributor mark?) on one side; C1 and engraved name/location on the reverse. The “C1” indicates the fork’s note designation — octave numbering varies between makers, so frequency may differ.
eBay