1
So, starting off, I have no idea and while ex-military, I am not a former naval person. Let's see if we can logic our way into something.  

1. It has military lines, so it's not a civilian conversion. It didn't used to be a Liberty Ship or something. 

2. Not a destroyer -- too fat.

3. Not an antiaircraft cruiser -- not enough guns.

4. Not an oiler -- too many guns.

5. Peering closely at the rigging, I see lots of support lines (cables? hawsers? wires? sailors always gotta be different). Maybe supports for HF antennae. Also a number of smaller antenna-like squares and spikes. Maybe communications support of some kind.

6. Big picture windows up front, suitable for admirals/generals to gather behind in wet weather. A number of protrusions that might be gun tubs, or that might be viewing balconies for when it's sunny.

Conclusion: amphibious assault command ship, class unknown

2 FoW, the name of the contest is "Name this Mystery Ship," not "Name this Mystery Type-of-Ship."

3

I don't have any idea what ship it is, but there are a lot of very curious things about it. The guns, for instance: those are 3" guns, not even 5's, which means about all they're good for is antiaircraft fire.

And there are a ridiculous number of places for lookouts on the superstructure. I'd wonder if this was a purpose-built picket ship, except that no one has ever done that to my knowledge.

Just based on the quality of the photo I think this is from the 1950's, and I think FoW is right: amphibious assault command ship.

4 I'm going with an Abdiel class fast minelayer

5

You picked a great one.  I actually laughed a bit when I saw it (Which given how things have been recently, was a relief.).

6 A different point: it's got a "dazzle" paintjob, which suggests it's British.

7 Ah, this is a good one.  I mean it's an actual ship and everything, not a building this time!  

Not sure where you're seeing dazzle camo, unless it's just the interplay of light and shadow.

Also, though I can understand why you'd think they're 3" guns, they are in fact 5"ers, they just look teeny tiny on that biiiig ship.

8 We have a winner on the text line!  Brickmuppet successfully named the ship at 348pm Pond Time. 

Which is good, since FDM seemed to enjoy dropping hints.  Naughty.

9

So TELL US already!

FDM look at the side just below the bank of lights, there's a dark patch. That's not the only dazzle but it's the easiest to spot.

10 I'm pretty sure that's just a shadow from the protruding bit above it.

Duck, my bad for hint-dropping.  It's just been so long since we had a mystery ship that I couldn't control myself...

11 I am pretty sure I never seen this particular photo of the ship before, but I needed to see only two elements of the ship before realizing what ship it was.

12 Now that the contest is over and speculation can be had...is it just me or does it look like a very small superstructure and small guns put on hull that was meant for a much bigger ship?

13 It's not just you, Ben.

14 Nobody's going to say, eh? (smug bastards)

15 New around here, but I enjoy torturing people too much, so I could not resist.

I know what this ship is. I'm going to drop two hints.

First, she has an awful number of 5-inch guns, doesn't she? I mean, if someone welded a Fletcher and a Gearing onto a lighthouse ship, you might end up with this. Lots of lookout points, 5-inch single and double mounts everywhere, and all on a real slow hull.

Second, when she was commissioned, her armament was actually much heavier than it is in this picture.

16 >Nobody's going to say, eh? (smug bastards)

And risk royally peeving our host? (As per the update above).  I think I'm on probation already.

17 I didn't see that update when I made that comment.

18 OK, I found it. At first I thought Google image search was out of its mind, but it did in fact have the right answer.

19 Well, you could have had asked on your blog and someone would have replied.  And maybe with the correct answer, too!