I would sell them together, Vic, since they may be worth a little more as an 'instant collection', as well as it being more convenient for you. The downside is that I don't think they're very valuable, since they were made in large quantities. Prince slugs are just about the only airgun-related item I've been able to pick up at bric-a-brac stalls in years of looking. Maybe £20 for the three? I don't really know. Ed would have a better idea, of course.