Basically it's a combination of the roughly 3" tall Legends class Optimus Prime and his trailer - which is a triple-changer that transforms from a trailer, a mobile weapons platform to a weapon's base - not bad for a little guy.
The Optimus Prime is no different from the other two or three Legends class Primes released in this series - including the Jetwing Prime and the Battle Steel Prime, save for the Armored Weapons Platform Prime being slightly lighter colored and his being sans the flame-detailing that only the Legends Jetwing Prime has.
Unfortunately the DOTM Optimus Prime Armored Weapons Platform did not make an appearance in the movie - it doesn't even come close to anything that appeared in the movie. It would have been interesting if Hasbro comes up with a trailer that appeared in the movie - the one that transformed into a weapon's storage unit that Prime drew his blade and his shield from when he first encountered Shockwave.
The DOTM Optimus Prime Armored Weapons Platform's blister card reads: "Optimus Prime turns to his armored weapons platform when his Energon blades can't quite cut it. The strike base is equipped with weapons far more powerful than the handheld variety he usually wields. The Armored Weapons Platform also converts to a mechanical exosuit if mobility enhancement is required. Decepticon foes beware - Optimus prime has become even more powerful!"
The best thing about the Optimus Prime Armored Weapons Platform was that it was on sale. He was purchased as a part of my Christmas splurge for PhP 600 (Roughly US$ 14) down from PhP 1,350 I believe (Roughly US$ 31). He's still available for US$ 29.92 (Roughly PhP 1,316) on Amazon - unless you want the Takara version which is available for a whopping US$ 63 (Roughly PhP 2,772 I have no idea how they're different).
Next up is the trailer. Ever since the Tranformers movies stated coming out, everyone has been looking for Optimus Prime's trailer. It took three movies before Michael Bay produced one. And even then Hasbro has only produced two official Prime trailers - to date - the infamous "Ultimate Optimus Prime" - which sucked - and this one.
Here's what he looks like in comparison to the Battle Steel Prime and the Jetwing Prime:
Optimus Prime himself is unremarkable in comparison with other Legends class DOTM Optimus Primes but he's actually quite a nice Legends class figure considering that if you unlock his hip he can twist it. He transforms into his semi and as earlier mentioned, he does not have flame detailing.
Which brings us to the Mobile Weapons Platform. The trailer's transformation is simple enough, it changes into a.... what can we call it? An exo-skeleton? Not quite because I doubt it if enhances anything. It looks more like nothing more than what it's called, a Mobile Weapons Platform. Optimus Prime attaches to it through locks for his feet on the bottom and a general lock on his back.
The final product looks like this - Optimus Prime with a missile launcher on top, two extended arms that can accept mechtech and other weapons (though there are other ports through the frame), and.... skates to move around.
The main weapon of the Optimus Prime Armored Weapons Platform is a cannon that comes from the top of the trailer that launches a missile. It attaches to his right arm-extension.
But with a little help from contributing Autobots and the recently reviewed ARK, you have this scary monster:
I forgot to mount anything on his feet.
The Optimus Prime Armored Weapons Platform also transforms into a Weapons Base. But there are two plausible transformations for this. Let's start with official one which looks like a mounted gun platform with side shields that smaller Autobots can possibly hide behind.
You can also launch Autobots from the forward ramp:
The unoffical version is actually mores stable as the official version tends to be a balancing act between the two wings atop a moving base.
It even looks more like a Weapons Base than the official version:
Let's start with... well he's so small. So far we've seen how nice a toy it is so wouldn't it be really cool if he were bigger?
Another problem is the trailer. When Optimus Prime uncouples from the trailer, the trailer cannot stand on it's own. It flops down lie discarded cargo.
The last thing not to like about the Optimus Prime Armored Weapons Platform is that when you transform his trailer into the "official" Weapons Base, he cannot use the platform standing erect. So the assumption is that you have to sit him down. The only way to do this is to actually compress his legs. He shouldn't have to do that which is why the "unofficial" version is actually better as he can reach the main cannon with no problems or compromises.
In closing, despite the fact that he's so small, which is really the biggest downer, it's a nice piece to have especially for the price. Of the three DOTM Optimus Primes released in the market, it is definitely the bet looking and the one that you can have the most fun with.