Ran into this image today. One needn't be able to read Old Church Slavonic in order to know who it is. A halo'd man writing in the company of a lion can't be anyone but St. Mark. That said, with a bit of patience one might translate the overlapping letters as well, from left to right.
св. is a standard abbreviation for святой, svyatoy, saint. The tilde over св means it's an abbreviation.
апост. is short for апостол, apostle, although it's hard to separate all the overlapping letters.
и, i, means 'and'.
Another jam, the letters are еван. a shortening of евангелист, evangelist.
