How to recognise partial text on mechanical indicators
If you are using an out-of-the box OCR engine, then there's not much you can do with significantly occluded letters.

However, if you are rolling your own OCR, say with some template-matching, then, there is nothing preventing you from learning/teaching partial letters and their valid combinations (like the 8-9 and 9-0 above). Just treat it as another letter in the set to be recognized.