I have said it before, that I have yet to see one of these fake cabs. No one has ever posted up here that they have seen, borrowed, owned, own a fake Diezel cab. There WERE cabs made for Diezel here in the states. It's the same cabinet maker that was making them for Bogner for a while, which is why 5 years ago, a Bogner and Diezel cab looked basically identical as far as the cab corners, handles, jack, jack location, etc.
I would not sweat it, if I was looking at one and it appeared to be solid and sounded good, I'd buy it. The chances of finding a new style German made cab on say, your local CL is nearly impossible. If there is a Diezel cab on someone's CL, it's likely going to be the older USA version. Even on the internet the new style cabs are rare, I believe I bought the very first german made 412FL cab to hit the used market back in '09, and I have only seen a small handful for sale since. I picked up another one, one of the NAMM show cabs a few months ago.