I found I still have these kicking around. All are attacted by a magnet. Apologies for the poor photo, my camera is not capable of close up images.
The single dart (.177) I think is 1950’s. Looks like a copper washed steel dart.
The galvanised steel darts (.177) are late 1970’s. If I recall correctly they were from Milbro. (Millard Bros, in Lanarkshire) These have seen some use and might have the odd scratch and dinged point.
The plastic fletchette type darts are circa +/- 1980. If I recall correctly they were from Sussex Armoury, in East Sussex. The dart looks like copper washed steel. These have also been used, but appear undamaged. There are two .177 and the others are .22. Again if I recall correctly they came in packets of 12, a clear plastic bubble on a card backing.
The Prometheus pellet (.22) is also circa +/- 1980. The head is steel (stainless?) with an opaque plastic skirt.
If this lot are of interest pm me with an offer, and they could be yours. (I’m in UK)