Tim is right, had to bite my tongue.
If it was a vernier it could not have a "glass" so must be digital.
Most likely, the "glass" is fixed in place with an adhesive, so careful prising MAY allow damage free removal.
If the worst comes to the worst,Mmachine DRO were able, until recently to supply at a reasonable price, new read heads for the generic digital callipers and linear scales..
Howard