Golden Skullcap Image
This image is the closest thing I can find to the mind-reading skullcap the party has — frankly, I’m amazed there was something this close available online. Like this image, the skullcap has a firmer band around the edge to hold it in place and the top part is the foil. The foil is thin enough to see a lattice of dark lines running through the helm, suggested in the image by the mesh peeking through where the cap is damaged.
When I think of skull cap, I can’t help but think of Excalibur.
http://static.guim.co.uk/sys-images/Guardian/Pix/pictures/2012/1/29/1327842169010/Nicol-Williamson-as-Merli-005.jpg
That’s exactly what I had in mind Follow Me, And Die!
That is an iconic skullcap — the lack of a band along the rim and silver coloring, though, made the above seem like a better choice of illustration.