Police may be on the brink of finally finding the remains of Judge Joseph Crater - and possibly solving the most enduring mystery in New York City history, investigators said yesterday. A letter probably penned more than half a century ago has pinpointed a spot under the Coney Island boardwalk where Crater - last seen leaving a Times Square watering hole 75 years ago - is buried, they said. The letter was written by an elderly woman who died of natural causes in June, they said. Upon her death, family members opened a safe-deposit box, where they found a letter...