The photo does not confirm your memories. The "exposure compensation" on the OM2 is just turning the film speed dial. There is no separate adjustment, just some +/- marks. ASA 1600 with no exposure compensation is exactly the same setting as ASA 400 with -2 exposure compensation. The dial maxes out at 1600 so there's no way to set 1600+1.
The OM-2s is an excellent camera, but suffers from the same battery issue as the OM-4.
It was not a design issue but rather an operational issue. Just like all these >20 year old cameras, there is no accounting for previous owner so make sure you have recourse. Also, there seems to be a "fix" -> Rick Oleson