Thank you for selecting Aerospace Aviation360 as your go-to distributor of part number LSD 8503 found under Disk Valve by William E Williams Valve Corp. The National Stock Number assigned to this part is 4820014473490, and the Federal Supply Class is 4820 Valves Nonpowered. Our website is owned and operated by ASAP Semiconductor, a leading distributor of aviation and aerospace part numbers like LSD 8503.