A bit about the C90
Sometimes the engines can tell you a lot about what type it is.
I flew LJ-511 (C90) for a while, and it had the PT6A-20s. They had very short exhaust pipes, and very little curvature. This made it easily identifiable because of the exhaust stains along the outboard sides of the nacelles. I also flew the A90 and B90 a few times. While these had the same -20 engines, the engine controls and features were quite different.
The C90A (and straight C90s with a conversion) had the PT6A-21s, and the E90 had the -28s. Those were the better engines (and airplanes) for many reasons. I never flew the C90A or B, and so am not aware of the subtle differences between those two.