Reset WLC 2504 to factory defaults

Via recover-config command

1. Connect a console cable to a workstation
2. Power on the WLC
3. Wait until User: prompt appears
4. Enter recover-config and hit Enter - this will trigger the recovery mechanism which will in effect factory reset the WLC
   

Via Boot Loader Menu

1. Connect a console cable to a workstation
2. Power on the WLC
3. Observe console output right after powering the WLC for the following message: Press <ESC> now to access the Boot Menu...
4. The Boot Loader Menu has 6 options:
   
   
   1. Run primary image
   2. Run backup image
   3. Change active boot image
   4. Clear configuration
   5. Format FLASH Drive
   6. Manually update images
      
      
5. Enter selection: 4 - and hit Enter, which will factory reset the WLC.

Sources:

WLC 2504 Reset factory via reset button
https://community.cisco.com/t5/wireless/wlc-2504-reset-factory-via-reset-button/td-p/3092417

Restore to factory default - cisco wlc 2504
https://community.spiceworks.com/t/restore-to-factory-default-cisco-wlc-2504/718825/1