Faulty battery, bad alternator, or both (photos)

Car is a 1974 Plymouth Scamp w/ stock 318.

So after installing my new battery (due to timing, I went to Walmart :banghead: ), I decided to check the battery.... (right after I noticed while driving that my amp gauge was solid towards the middle, then pegged all the way to the right (+40), and slowly went back down).

When it settled, it landed in the negative.

I decided to do some testing.

With the car off, I'm getting a reading of exactly 12 volts at the battery. Shouldn't this be higher?

I started the car, no accessories turned on, and here is my battery and amp gauge reading:

battery:


Gauge:


NOW....I then decided to rev the engine a couple of times, and turn on the lights. Here is the result of that, with ONLY the lights on:

Battery:


Gauge:


So my question is, do I have a bad alternator? A bad battery? Both?