A cavity resonator and antenna system, it was. The toroid base was the cavity resonator, and the cross was the feedline and dipole antenna. Fitted into the proper parabolic reflector and shock excited periodically, it would excite a similar antenna at the site of Murdoch's Hoard. This would continue to oscillate for many milli-seconds after the shock-excitation. If the Key were switched to a receiving system--a detector--the answering oscillation of the sympathetic system would act as a radiator. Directive operation--scanning--of the parabolic reflector would give directive response, leading the user to the site of Murdoch's Hoard. How men must have fought to find Murdoch's Hoard in the days long past! * * * * * Cal Blair considered the Key. It would lead him to nothing but roistering and space travel and the result would be no gain. Yet there was a certain scientific curiosity in seeing whether his deciphering had been correct. Not that he doubted it, but the idea sort of intrigued him. The project was at least _unique_. He looked up the history of the gadget in an ancient issue of the Interplanetary Encyclopedia and came up with the following description: Murdoch's Hoard: An unknown treasure said to be cached by the pirate Hellion Murdoch. This treasure is supposed to have been collected by Murdoch during his years as an illegal neurosurgeon. For listings of Murdoch's better known contributions to medicine, see.... (A list of items filled half a page at this point, which Cal Blair skipped.) Murdoch's Hoard is concealed well, and has never been found. The Key to Murdoch's Hoard was a minute cavity resonator and antenna system which would lead the user to the cache. No one has been able to make the Key function properly, and no one was ever able to break the code, which was engraved around the base. The value of the Key is doubtful. Though thousands of identical Keys were made on the Franks-Channing matter reproducer, no scientist has ever succeeded in getting a response. Engravings on the base are obviously a code of some sort giving instructions as to the use of the Key, but the secret of the code is no less obscure than the use of the Key itself. The original may be identified by a threaded stud protruding from the bottom. This stud was eliminated in the reproduction since it interfered with the upright position of the Key when used as an ornament. The original was turned over to the Interplanetary Museum at the time of Channing's death from which place it has disappeared and has been rediscovered several times. At the present time, the original Key to Murdoch's Hoard is again missing, it having been stolen out of the Museum for the seventeenth time in three hundred years.