It's missing the face and it looks like the glass windows were replaced at one stage (I think around 1904, because the stamp of a jeweler from that period is on the back).
That Jeweler's "stamp" would indicate that
the mechanism was cleaned, oiled, repaired and/or adjusted.
The top portal is for the clock “face” (hour-minutes) ….. but what is the bottom portal for? A “day” number indicator?
Anyway, you can probably find an hour/minute “face”, hands, etc. that will work on your clock via a web search.