UG982-06 Dell System Board (Motherboard) for OptiPlex GX520 SDT (Refurbished)
XG309 Dell System Board (Motherboard) for OptiPlex GX520 SFF (Refurbished)
Dell RJ291 - Desktop Motherboard for OptiPlex GX520
Amazon.com: 0Wg233 Dell Motherboard For Optiplex Gx520 : Electronics
Original Dell Optiplex Gx520 SFF Motherboard 0XG309 Includes Processor Small form factor SFF only GX 520 (Used) Condition USED, tested 100% Working FOC: P4 3.0GHz LGA775 Processor | Lazada
CN-0RJ291 For Dell Optiplex GX520 MT Motherboard 0RJ291 RJ291 LGA 775 DDR2 Mainboard 100% Tested Fully Work - AliExpress
Dell Ut806 System Board For Optiplex Gx520 Sff-Ut806 - Newegg.com