Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 6520-111-21 found under Casing And Core Tachometer by Jones Instrument Corp. The National Stock Number assigned to this part is 6680003148015, and the Federal Supply Class is . Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like 6520-111-21.