And all of this predates the Internet or digitalization of manuals and data sheets by decades. So unless someone has scanned a paper copy, you are not going to find anything.
The contactors no longer exist in any format, though you may be able to scrounge around on Fleabay for old parts. I wouldn't bother though, because THOSE parts will all be old as well. The ITE/Goulds 5600 series was taken out of production 25 years ago and even before that, Siemens had jettisoned the old Goulds/Rundell starters to Telemecanhique, who then totally dumped it when they bought Sq. D, so it's likely been more that 30 years since those parts have been made by anyone.
You can still order replacement MCC buckets for 5600 series MCCs from Siemens that will plug in, but they will have Siemens breakers and starters in them (the breakers may be almost exactly the same however). The tricky part will be finding someone within Siemens that is aware of that! Their MCC specialists are supposed to know, but that's kind of hit and miss around the country.
http://www.industry.usa.siemens.com...nters/Documents/CCBR-MCCAR-0813_PRINT_low.pdf
Eaton also sells aftermarket retrofit buckets for 5600 MCCs that will be built with Cutler Hammer parts, but I'm not sure of the UL listing of those because UL listing of MCC units must include testing IN THE STRUCTURE, which Siemens owns the rights to.