Quote from Lieutenant Disher in Mr. Monk Makes a Friend
Lieutenant Disher: Captain! Murder weapon. Boys found it under the stove. Hal Tucker: The handle's cracked. Is that from hittin' the guy? Lieutenant Disher: Yeah, that's right. The serial number's been filed off too. Makes it almost impossible to trace. Captain Stottlemeyer: Are you reporting to him now? Lieutenant Disher: [to Stottlemeyer] The serial number's been filed off. Makes it almost impossible...