Refurbished: Dell Optiplex GX520 Small Form Factor - 2.5GHz Intel Celeron Processor - 2GB Memory - Windows 7 Home Premium (1 Year Warranty) - Newegg.com
Vintage Dell Optiplex GX520 Series DCCY Pentium 4 3.00GHz-No Hard Drive | eBay
GX520 | Dell Optiplex GX520 Computer Base Unit | Refurbished | Computers · PC User
Oldest desktop of the day with Linux: Dell 0X7841 (OptiPlex GX520) : r/Hardware_for_Linux
Dell Optiplex GX520 Intel Pentium 4 2.80 GHz Desktop Small Form Factor Base Unit PC