Key icon definitions?

I've searched this forum and in-app help, but can find no comprehensive definition of the key icons.  Yes, there are references to double key and gold key, but nothing that brings them all together.

I have single keys, double keys (blue and gold), grayed out single keys, skeleton keys, envelopes, pen-with-[globe?].  Images below.

The closest I have found in help are subkey descriptions in "Working with Subkeys" but those shown are in the properties box under Usage and do not match the icons in the key list.

Does anyone have a list of icons and descriptions?

Subkey table from Help