Not only is it copper, it's actually the copper side of stripboard, specifically the larger 3.5 mm (0.15 in) pitch, and it's the same in ST, PP1, PP2, & ESB:
[ATTACH=full]220321[/ATTACH]
PP1:
[ATTACH=full]220322[/ATTACH]
supertrooper:
[ATTACH=full]220323[/ATTACH]
PP2:
[ATTACH=full]220324[/ATTACH][ATTACH=full]220325[/ATTACH]