I'm quite familiar with the vintage 1970's era Atlas/Roco O scale product line as the lead consultant on the US end was Ted Stepek, someone who along with John Armstrong hosted our Friday night model RR group for many years. Ted did advertising art for Atlas, prototype research, and co-authored several Atlas layout design books with John. I had the opportunity to see the pre-production models running on Ted's O scale 2 rail layout and the art work for the lettering before the models hit US shores.
Ted acquired actual PRR prototype drawings for the X43c box car and sent them to Roco in Austria. The car is spot on for Pennsy's X43c. Similar riveted 8' door, diagonal panel roof, improved dreadnaught end 40' box cars were produced by other car builders, but that cast on trust plate is pure PRR. The Atlas 40' plug door box car and stock car were not based on any specific prototype. To hold down production cost Roco utilized the car end, roof, and underframe tooling they created for the box car. The 52' gondola was modeled using PRR G32 drawings, but was slightly reduced in length for what I believe were clearance issues associated with Lionel O22 switch housings. I dn't know for a fact but was told the ore car was based on a B&LE prototype. The 4 wheel bobber appears to be based on a Reading prototype.
The 1970's era AtlasO cars came ready to run with plastic trucks and lobster claw couplers. For conversion to two rail Atlas offered replacement metal wheel sets and bolt on scale couplers. Unfortunately to this day Atlas continues to use the patented snap on lid/hidden screw coupler pocket - the one with screw locations not fully compatible with Kadee's (if you use the Kadee pocket and Atlas screw locations the pocket with stick out past the end sill - I prefer to drill & tap new holes for Kadees).
Back in the early 1970's the Atlas scale cars were a nice addition to freight trains typically filled with Athearn or All Nation kit built cars and US hobbies/Max Gray painted brass. The Atlas line set a new standard with underbody brake rigging and door hardware- details not found on brass imports or Athearn/All nation kits in the early 70's.