What's the minimum item level where sockets appear?

After several days worth of research, using the items offered at the Auction House as a guideline, I was able to determine that socketed items are generally available as low as level 15. It does not seem to matter what item is in question (armor, rings, weapons, etc) - you must be level 15 to equip something that contains a socket.

While the answer that level 15 is the lowest level is generally correct, you can in fact find legendary items that are of lower level.

For instance, the legendary item "See No Evil" is a Monk head gear, with socket, and can be commonly found at level 10.