Dear Amit, you seems to be right, the Ry. seems to consist of two digits and therefore ought to attributed to Muhammad Shah. In that case the mint would be Surat. It is only incase of some of the later rulers (viz.: Shah Jahan III, Shah Alam II) that coins of this type were struck at other places than Surat it self.
The exact Ry. on this coin is not clear, perhaps an enlargement of that part of the die may be provided.