"huckleberry" pattern sentinel. Titan legs, titan feet, hellhound turret (including the chimera turret), assault bike heavy bolter ammo feet (cut from the heavy bolter), and the gun is from a dreadnaught. Based on the then rare 60mm flat base.
The hatch is from the imperial accessories sprue, and the driver is a valhallan heavy weapons gunner.
I built a similar one with dread feet, predator turret, and the old metal sentinel's assault cannon. The waist on mine is a spare marine bike headlight and flak guard, and half of a tire. The driver is the old chimera driver.
Here is a picture of mine