Mh this is weird because the C-box is supposed to be 512k.
I think this is just a C tune that was concatenated to a 1024k file. I've done this before to run a C box file on a D box.
By looking into the file I also see this to be the case. Also this is a Revotechnik file, based on this string in it:
(c) 2003 Revotechnik Patent Pending
Try this then, I read it both 1mb and 512kb as wasn't sure the file size.. It worked both ways reading it, I have probably posted the wrong one.. here you go