I would strongly advise against Verizon CPO. I will make a very long story as short as possible. I purchased 5 iPhone 5 units last year. I had to ultimately get 10 to find 5 that were (marginally) acceptable. I was not being overly picky by any means:
a) 2 arrived with "stuck" home buttons. They would not depress at all. It was almost as if they were glued in place. They were unusable.
b) 1 had an obviously aftermarket screen and upon touching the screen you would see a major rainbow in about a 1" diameter around your finger (regardless of where you pressed on the screen).
c) 1 had a bad mic, and could not be used handsfree. If you used bluetooth or a headset it would work, but not the mic alone.
d) 1 had a "plugged up" lightning port which caused problems with charging.
e) 4 had well-used batteries. I used an application to check battery life and they were fairly low, I don't recall the percentages now.
f) 1 had a screen that was not seated properly (you could see a ridge on 1 end, the other end was flush).
As mentioned, I had to get 10 phones to keep 5. Ultimately I accepted those with the fewest problems (I kept those with weak batteries, and the one with the plugged lightning port that I was able to partially clean out). Anyhow, not a single unit was really to the level I would deem "certified".
To top it off, I took my nieces with 2 of those that I kept with poor batteries to the Apple Store about 3 weeks ago. They tested 1 of them, and found that it was covered under the battery replacement recall, even though I had entered that serial number on the Apple web site and it said it was not eligible. No complaint, they fixed it for free, and my 1 niece had a new battery, and uncle saved $80.
But my 2nd niece's phone was not eligible for the free replacement, so I said fine, I will pay the $80 fee for her phone (I had expected to spend $160 that night, so I wasn't upset). We were told both phones would be ready in an hour, so we went to get a bite to eat. Upon return to the store, we were told that the 2nd phone would not be repaired because it was obviously repaired in the past with non-Apple parts. They put the 2 phones side by side, and you could definitely see the differences. So I had to contact Verizon (wasted about an hour), but they then sent a replacement.
Verizon insisted on 2 occasions that there CPO phones come from Apple. I absolutely cannot believe that statement.
Told you this was a long story...and I just told the short version!