Playstation3 Full Backward Compatible Model CECHA01 firmware v3.55 - Reballing Genius LLC
Downgrade any CFW PS3 to 3.55 or any other CFW - DIYProjects.Tech
PlayStation 3: Sony releases Firmware 4.86 for their 13 year old console - HFW 4.86 released, SEN Enabler updated & PS3HEN to be updated soon due to no kernel changes! - Wololo.net
How to Downgrade a PS3 to 3.55 with E3 Flasher (EASY!) - YouTube