Possible..? Untethered JB on ATV2 without SHSHs or older JB

Hello everybody…!

I am dealing quite a while with jailbreaking ATV2s. The only question, I don’t really get an answer (is asked Mrs. Google quite often) is:

Let’s say I have an ATV2 with iOS 5.2.1 that has never been jailbroken and I have no SHSHs…is there an way to put an UNthethered JB on it…? A tethered one is of course no problem…

I found a trick to integrate SHSHs from another device in a signed IPSW, worked well until the point where I restore it on the ATV via iTunes. It always ended with an error 1600. Usually error 1600 results of bad USB-cables or wrong DFU-mode. In my case, this can not be true because I can use this USB-cable to jailbreak 3 other ATVs and I can restore the original Apple-FW on it without any problems. And I use iFaith/iReb (latest version) to put my ATV in DFU mode…

Thx in advance,