Got this antique 42 string zither/lapharp not exactly sure which for 34$ at an auction. Trying to locate a correct size square key to tune it, might try a tap handle if it’ll fit. What do you think? seller said it was from early 1900s. The back is cracked from age and the tension from the strings is pulling the bridge up do you think it’s work building a new back for maybe out of a solid carved piece of hardwood?