The first highlighted detail is at the left, on the truck sideframe. Note the crosshatch pattern and the two lines further down the sideframe. Since the sideframes are cast, these raised details are features of the sideframe. They do not appear to offer any significant structural advantage. It is possible that they are decorative, but I have not seen anything similar before. The truck is a Dalman two-level type.
The next detail is above the truck, on the side sill. It is interesting how one leg of the grab iron is attached integrally with the sill step. This is more common than most modelers might think and is a nice detail to model on cars where it is appropriate.
Moving to the right, note that the cast roping staple loop has cracked and broken off, with only the mounts remaining in place. I don't think this is all that common a condition, but it could be modeled. I believe that the car is a Reading composite gondola, as offered in HO scale by Funaro & Camerlengo.
The last detail is at lower right. The trucks and wheel faces were covered in the greasy soup that lubricated the axles in pre-roller bearing days. This attracted dirt, grime, and anything else that would stick. You can see a thick, coarse coating of such material below the journal box lid. This can be replicated by repeated applications of chalks and powders with those from Bragdon being the most resistant to disappearing after addition of a flat coat to seal them. It might even be interesting to add fine granules (fine in reality; more coarse in HO or whatever scale you model) to the surface of the wheel faces and below journal lids before painting the trucks and wheel sets. I may give this a try in future.