You can search old posts for keywords. This is a super feature. I entered AT3 and came up with TCP1002 (?) discussion with Richard in which they discussed DE's and AT's.  It looks like DE3 Should be AT3. I haven't a clue where DE4 would be. Specifically TCP/Richard  said:

"I asked how many drills we had at DE and he said 3. I asked if they were all at DE or loaned to other projects and he said they are all at DE being used by Noront. He said one drill was at DE2 one at AT3 and he wasn't sure about the other.

I asked if we had a DE3 and he explained the following.  The project and area is called Double Eagle. We've found ore bodies in two arears and they are called DE1 and DE2.  We are currently drilling at AT3. He said the AT comes for the Air surveys they did (I can't remember the exact term he used).  So once they find an ore body it will be changed to D3.  I asked if there was a AT4 and AT5 and he said they are reviewing this now and cutting lines to go in and drill."