First you need to state if it is a 6M alto, a 10M tenor, or other M series saxophone.  Then it depends on the condition of the horn, and how much repair work it might need.  The year of you horn should be 1958 - 1959, so it is well past the prime value years for the Conn M series horns.  More detail is needed, maybe even some photos would be needed for any semblance of accuracy.
Let us know what version you have.