The above 2 pics...
represent two different cockpit views of 2 different Albatros D III's .It is the only views I have from my reference material that shows something beyond just a tachometer.
There were other instruments on board even during WW1.I suspect that maybe the aircraft in the Smithsonian doesn't have them installed therefore no one shows them being on board.
The first instruments would be just stuck anywhere struts ,tubes etc....During WW1 things became a little more organized and there was some indication of primary and secondary instrument placing :such as airspeed,altimeter,tachometer, VOR,ILS oops... got carried away there. Secondary instruments like pressure gauges,temp ,content etc only became important when the engine was about to quit or run out of fuel(then they became real important)