The purple single barrelled gun is Tiptop. His barrel is the longest of any of the dual Targetmasters: Why it is will shortly become apparent. To transform him into a robot fold the gun barrel back into the body of the weapon and stand on the front of the weapon. His robot mode has the 5mm peg used for holding him on it's chest (Chest cannon!) He's moulded with a set of six missiles in a box on each shoulder. Both arms and the waist are painted orange while the upper legs and face are a burgundy purple similar to the colour used on Quake.
The Black dual barrelled gun is Heater. Fold the twin barrels back behind the robot's legs and stand him up to reveal his robot mode. He again has a chest mounted peg, with blue upper legs and pointed shoulders and a red waist & face.
Unlike the other dual Targetmasters, Quake seems to only have one 5mm hole for attaching the guns to, meaning they have to be combined using the 5mm hole in the top of one of them in connection with the post on the other. However there is a second 5mm port and that's currently occupied by Quake's tank barrel. This piece can be removed (and then lost, as many of the Quakes on eBay testify) revealing a 5mm peg hole, set into the body of the tank rather than the turret, which allows the tank's gun barrel to be replaced by one of the Targetmasters. Now to my mind the gun barrel is one part too many. It's function is adequately served by the Targetmasters, especially Tiptop which makes a great tank gun barrel and would even better if he were coloured black. Indeed the only point that the instructions show the gun barrel is a side on picture of the tank mode, and even there it's not clear if it's the gun barrel or a Targetmaster. My thinking is the gun barrel is a late addition to the toy.
Transformation: Remove all Targetmasters and the tank barrel. Split the back of the tank in two and fold the treads forward, via a hinge on their front corner, until both sides of the tank point out the front of the tank as the robot's legs. Fold the feet down from the legs and stand with the underside of the tank facing forward. Split the turret in two and fold out to the sides to form the arms. Fold the hands out from the arms and peg in the Targetmasters as weapons.
Quake's robot mode is surprisingly large for so small a vehicle mode with it's height effectively being double the body's length. His chest features some Prime like window detailing and is dark blue, which doesn't sit 100% well with the burgundy purple, now used for his outer legs. His inner legs, arms and head are grey with an orange face. The arms turn at the shoulders and fold back a bit as part of the Transformation. In addition to the hands, he has a 5mm port on the outside of the right forearm, a useful home for the gun formed from the tank turret, and another one you can use for storing weapons in the middle of his back.
I like Quake, I think he's the best of the Dual Targetmasters with the ability to use the Targetmasters as different tank guns being a major selling point. The inclusion of the extra tank barrel and the lack of a second spare hole to attach weapons to in tank mode muddy the issue a little and make it less obvious that this is what you should be doing. And make it harder to find a complete one on eBay now!
Quake was sold in the USA & UK as a carded toy in 1988. He was not sold in Japan.
I've seen Sea Team Minicon Oceanglide pull the same transformation trick with the turret becoming the arms but still have a revolving turret. I await a new version of Quake with a revolving turret that incorporate a pivoting 5mm port for mounting a Targetmaster gun on.