This may call for a visit to: THE BUNKER OF DOOM ! http://www.bunkerofdoom.com/xfm/
...where you can find the answer to almost any question. In a left-handed way. Sorta'.
Poke around long enough and you'll find a link to the AudioPhool site, then stumble across the TechoPhool page: http://www.audiophool.cjb.net/Techno.html
which I think you'll find amusing, and a link to this dude... http://www.audiophool.cjb.net/Misc/53_freed.djvu
Portions of the Freed transformer catalog from 1953.
Note: My Deja' Vu browser plug-in choked on this file. Download it to your desktop then open it with the standalone DJVU viewer.
On page N-75 you'll discover the Freed DC6A was not a specific transformer, but the case outline and mounting spec for their "15 Pound" transformer offerings. Translation: There were multiple flavors of the Freed DC6A transformer and (at least in 1953) none of them show as 600-0-600 VAC. For that you needed to jump to their DC-7BL transformer outline. (?) Don't be afraid to poke around either site as your efforts will be rewarded by a virtual plethora of schematics and construction tips for 50's vintage DIY Hi-Fi Amplificators.
Assuming that's the sort of thing you might be interested in...............................
BTW: This is what hard-core home audio looks like: http://www.jogis-roehrenbude.de/Leserbriefe/Drehko-Stefan-6C33C-Amp/Stefan-6C33-Amp.htm
N4NYY tells me he's built monoblock amplifiers nicer than this, but unfortunately they were all in his dreams......................