Owners manual (incomplete)
Information on the top of the line CDP X777ES: http://www.thevintageknob.org/SONY/sonyes/CDPX777ES/CDPX777ES.html
Information on the Sony ES Series in general: http://www.thevintageknob.org/SONY/sonyes/sonyES-main.html
CDP-555ESA site (lots of photos): http://www.kameson.com/audio/CDP-555ESA.htm
Another CDP-X555ES site: http://www.hifido.co.jp/KW/G0401/J/0-10/C07-35310-10120-00/