Not diecast, but laser cut steel is close enough, right?
My wife gave this to me for my birthday, and I just put it together, so now you get to see it. It's a Metal Earth model. They come in a flat cardboard package like so:
Open it up and you get 2 sheets of laser cut stainless steel and a sheet of instructions.
To assemble, you wiggle the pieces loose from the sheet and then shape/bend/fold them into the appropriate configuration. The individual pieces are then assembled by putting tiny tabs in tiny slots and bending/twisting them with needle-nose pliers or tweezers.
This particular model has the outer skin on one half and then the skeleton on the other half.
You can see in these pictures that the nose of the skin was hard to really get into the right shape, so it's not perfect. But it's one of those cases where it actually looks a little better in person than in pictures because of the size of the model.
Those little engines are remarkably fiddly since they're only about 1/4" long. Even so, they're way over scale compared to pictures of the real thing.
The model is about 4.5" long, making it approximately 1:2000 scale, if I have mathed correctly.