Size Two and Size Three bat-eared insulators made in Imperial Russia. Ear-holes were used for a safety cotter-pin. As far as I know this "bat-ears" design is of german origin (Judging by available photos and Porzellanfabrik Hermsdorf-Klosterlausnitz production catalogue). The oldest known russian bat-eared insulators date back to 1879. As far as I know, this design was used at least in Germany, Poland and Russia. Any additional information is much appreciated.