Here's all I can suggest on determining whether it is a 4G, 4T or 4N. If you are the original purchaser you probably had to set up an account on Headphonia.com. When I go to their website and enter password for my account, I can see all of the purchases I have made. It lists whether 4G or 2G on mine. Headphonia offered the 4G first, I got mine Jan 2012. Later they offered the 4N and 4T but I don't know exactly when they started doing that. It is possible to open the Arrow (to change battery etc), maybe there is an indication of some kind on the op amp, if can identify. the 4G had an OPA2209, the 4N had an AD8397 and the 4T had an AD8620. You could contact Robert, at Headphonia, there is contact email at website, he probably has the info on what you purchased but he is a busy fellow, especially now that he is working on the 5G. Perhaps another headfier has more info on how to identify. I would be interested in the 4N or possibly 4T but I will probably wait on this until Headphonia offers reconditioned ones probably this fall.