I'd bet 99.44% that you have a turbodiesel.

SDs that year all had turbos, and it's really unlikely that the engine was swapped for a non-turbo. I can't think of one reason to do so.

If the power increases noticeably at around 2,000-2,500 rpm, that's normal turbo boost.

The Turbodiesel badge on the trunk is probably missing.

My 86 300SDL has no badges on the trunk, just the three-pointed star. Previous owner(s) removed the 300SDL and Turbodiesel when they had it repainted, and never put them back on.

I think that Mercedes cars in Europe don't have badges like in the US.

Enjoy the car, it's one of M-B's best.

Jim