Antec Basiq Power 550 Plus - semi-modular PSU with associated leads and power cable
Details here - https://www.atxpowersupplies.com/Antec-550-Watt-Power-Supply-Basiq-BP550-PL...
Manual here - https://images10.newegg.com/UploadFilesForNewegg/itemintelligence/Antec/BP5...
Was working OK when replaced with upgrade a couple of years ago