I'm on a trip visiting my niece in Ireland (her husband has been transferred to his company's plant in Cork for a year or two). I found an advertisement on an online marketplace for some glass insulators. When I went to pick them up, it turns out the seller also had some porcelain ones, among them this marked Bullers and a P & T. He found the Bullers on the now defunct East Cork Railway. He also had a railway signal, other RR stuff, machinery, and signs in his sheds.