Ah-ha, well done Geoff, you have brought up a point that I was wondering about. So to be clear here and as an example, if I was with a group of Marines and the challenge is made with their Marine coin, then I would be OK with my MacLeod coin? What is the form for those that have no challenge coin (I don't mean that they have forgotten it, but they just do not have one)?

Thank you every one for the advice given and yes, I can see that things could get expensive!