What Kind of view finder does my old Nikon D70 use, a pentaprism or pentamirror?

I was cleaning my old D70 yesterday since I had recently gotten back from vacation. I got a little mud on the front of my D70 caused my me almost slipping into a lake lol. The mud came off and all is well.

However what I noticed though while cleaning the view finder is that with the battery removed from my D70 the view finder is blurry and dark. But if I hold the camera up to my eye and insert the battery the view finder brightens up and comes back into focus.

I did this same test with my D7000 which I know has a Pentaprism. Once the battery was removed the view finder got dark and blurry. However once the battery was reinstalled the view finder brightened up and came into focus.

However when I did the test with my D3100 the view finder remained bright and in focus with the battery removed. The D3100 has a Pentamirror.

So anyways does this mean the D70 used a Pentaprism? I checked online. DP review said in the specs that the D70 used a Pentaprism but Nikon's USA site doesn't say what the D70 used in the specs.

This is just something that made me curious. The view finder on the D70 seems to be brighter and slightly more detailed than that of the D3100 which makes me think the D70 may have used a Pentaprism.