Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number 1557 found under Pin Eccentric by O F Mossberg And Sonsincorporated. The National Stock Number assigned to this part is 5315015767008, and the Federal Supply Class is 5315 Nails Machine Keys And Pins. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like 1557.