That's the air pump.

With the turbo generator right above the air pump. Not sure when the air pumps were added, but thinking maybe late 60s or early 70's.

Actually, we have 4. HEPC 46 (ALCo 1920 0-4-0ST) 62.118 & 62.129 (Duro Dakovich), Atlas Steel 30" gauge fireless (Porter 1943). 5 if you include the 3.5" gauge 4-6-2 on display. 46 and the 2 new engines will be outside together for the first time for our event in week. Will show a contrast in the designs.

The air compressors look like they are of German manufactured compound type

We did take a look at it before we moved them, and it is possible. I'll try to remember to get a pic of the plate on the pump itself when i'm out there Saturday.

The first word on the plate looks to be "Deutsche". Looking in a book I have from Meiningen Dampflokwerks, the compressors they use look identical. The gizmo on the top head is a mechanical lubricator. The earlier picture is taken from an angle that makes it look like the dynamo is mounted on the airpump, but it is really mounted on the smokebox....

The top line says "Deutsche Reichsbahn," the name for the post-World War One nationalised German railway network before the East/West partition, and retained by the East German network after partition. The Reichsbahn name wasn't generally used by itself until 1937, after earlier uses of abbreviations of Reichseisenbahnen and Reichsbahn-Gesellschaft.