A folder called "TBot1" can be found in the model textures files from the playable Half-Life 2 Beta files, in a folder called "obsolete". This is likely the textures for the early "mech" or (ro)bot from the Weather Control story fragment, a very early NPC, since it bears some similarities with Dog in design, mirroring the Weather Control story fragment covered above. Since Dog is said to be one of the few concepts that went from the first sketch straight into the game with relatively few changes to the design, it could be assumed that the Weather Control mechs are two legged and bear similar colors and same body part plates than Dog, since he was made from scraps from different metal sources, such as Combine metal (an old texture file for Dog also shows a "15" like logo also found in the TBot textures).
The textures also suggest a slightly battered/rusty robot, show round eyes that recall the City Scanner's eye, and therefore Dog's head, and is overall yellow-colored and seems to have paws-like feet and two legs, also like Dog. The model is however missing, and it is next to impossible to guess its shape from its texture files. The "1" in the folder's name also suggests that there was probably other versions, thus other colors or other conditions, for example non-battered textures. Other texture files suggest that it had an antenna and was equipped with a flamethrower and that some of its intern circuits were to be visible and blue, like the early Combine Dropship, the Crab Synth and the Mortar Synth. The files also suggest a "collar" made of green fabric, with the same fabric on one shoulder and the thighs, which seems peculiar, although it is another example of the old concept of the Combine recycling human materials.
This "TBot" ("bot" implying "robot") seems more mechanical than Synth (sporting several cogwheels and pistons on its bodywork), more in the "Combine recycling human materials" mood of the very early Half-Life 2 storyline and very closer to the "mech" from the Weather Control story fragment, therefore its model was likely an ancestor of the two-legged Synths of big size, the Combine Synth Elite Soldier or the Combine Super Soldier, with strangely-looking heads.