My guess is copper. They have always been very careful to say to use coolant not water. That and it looks a copper "PD360" on their site we got: http://www.syscooling.com/products/Radiators/54.html . The two aluminum radiator's they show selling are much smaller then the one with kit.
I could be wrong if they used a specialty one for miners, but I'm highly guessing its their standard.
I could be wrong if they used a specialty one for miners, but I'm highly guessing its their standard.
Yes, you have to assume its copper or there are copper components. In several points in the listings (all changed by now) there has been a mention of copper on both the radiator and the fittings [internal coating]. You can see within the chamber of the radiator that there is definitely some form of dark orange coating, which may be brass or copper. So tldr, be safe and assume there is copper and aluminium within the same loop.
Any luck finding out what the radiator is made out of?
See below. Suggesting its all aluminium, so the coatings we see must be brass [which is fine].
The radiator SC-BC1 watercooling kits uses is aluminum.PD360 radator is copper,only PD series radiator is copper.
Like the picture on your site, its golden in the threads and in the lower chambers. http://www.syscooling.com/products/Radiators/54.html. Looks exactly like my very early batch 1.
Threads looks brass in that pic. to me, also it appears thicker at 45mm (from specs. listed) compared to the one I got that looks closer to 25mm.
.We test pumps and radiators with air compressor,put them in water partly or wholly to see whether there is bubble getting out,whole process is about 10 seconds. 
