My friend in Uruguay sent me some pictures of one of the two Iron Clad insulators he recently found.

As you can see, the name Warden stands out quite nicely. I "googled" Warden and the brief note states they made stoneware in the 1870's [London, England]

It has elsewhere been stated that Iron Clad insulators were used to prevent the porcelain insulators within being broken and the pieces being used as arrow or spear tips.