I bought two and neither of them opened past about 30 degrees, so I couldn't have started to use them. If I forced them then they started to 'unwrap' the rolled portion that forms the hinge. 10 seconds with a Dremel and they're fine. Now to test them on a tin...

Oh, and just so you know, I paid NZ$2.50 each (about US$1.72). Some things are expensive on this remote island.

A