Quote Originally Posted by Xmas View Post
a pair of needle nosed pliers and a file will do instead of a spanner wrench, big pliers for large rings, small pliers for small rings.

You file the pliers ends for exact fit in ring...

And take great care
A piece of sheetmetal ground/filed to clear the glass and fit into the spanner notches is a far better solution. I'll forgo taking something apart rather than use the pliers approach, it's no substitute for a spanner and a very good way to ruin both the pliers and whatever you are trying to take apart.