88mm Flak 37

The second diorama I made is a scene in central Europe, with an eighty-eight bringing it's guns to bear during a demonstration/bombardment, during the pre-world war 2 arms race. It was a very fun but rushed build.

The 88mm FlaK was less effective against low-flying aircraft than the 20mm FlaK, less effective than the 128mm FlaK against high-altitude bombers; less mobile than the 7.5cm PaK, which could take out almost as many different targets; less powerful than the 15cm K, the standard artillerypiece of the german military. However, it was one of the only guns that could do all three, earning the name AAA or "Triple A gun" (Air, Armor, Artillery). And unlike larger guns, like the 128mm FlaK, it could move quickly, and could still do massive damage to most targets.

Good full view. You can see the rear bogey, or wheel-sets.

It was originally devised in 1918, as a medium air defense gun; as tanks were not yet common, and artillery pieces were being built larger and larger, not worrying about mobility. 

From here, you can see the front shield. It was very thin, designed not to stop direct hits, but deflect shrapnel and small arms fire.

During WWII, the Germans put the 88mm gun to great use, first as a AAA gun; then they adapted it for an anti-tank role; then put that in a tank.

By the end of the war, almost every country involved had their own version of it: the Russian 85mm gun, the U.S. 90mm gun, and many more examples which I can't think of as of now.