Product details here:
http://www.metz.de/en/foto-elektroni...chreibung.html
Handbook(s) at the bottom of this page:
http://www.metz.de/en/photo-electron...n-manuals.html
Note that the price on offer from Calumet is the same as you'd normally pay for the lower powered 48AF-1. One of the arguments normally used to justify why you shouldn't use 3rd party flashguns is that it may not be compatible with future cameras, the 48/58AF-1 models get around this by having a USB port on them to allow users to upgrade the firmware as models come on the market or to add improvements. Metz build quality is top-end.
Don rates Metz stuff very highly, that's why I bought one, no regrets, even if I did pay full price!