It was similar to this with three small plastic "cartridges". But as I stated in the OP it was conical with the large circumference around the mouth and nose but not covering the eyes, and the point of the cone forward. Think about pictures of the plague masks from the middle ages.

This training mask is in two pieces with the valves on the inner silicone mask over the mouth and nose, and an outer neoprene or fabric mask holding the inner part in place. The outer part is variously styled apparently. I gather from reading that the object is to add resistance to the effort to breath thus building up the breathing muscles of the diaphragm and chest. It all sounds a little S&M.