It's part of the sweep arm from Transcriptors and Michell record players (early Michell record players are transcriptors record players made under license). Several different models.of the sweep arm contain the dart and toe spike parts. One of the versions is also the stabiliser part for the jetpack and another of the versions contains the part for the super trooper blaster. If you search the forum for 'sweep arm' you'll find several threads. One by Art Andrews contain a breakdown and comparison of the different versions. None of them are cheap as none are now produced so if you consider you may have to buy four in order to achieve the four darts and toe spikes the price will soon add up. Couple the fact that it's easier to pay for them than find them and you'll see there may be a road of substantial length to tread.