Diamond-I mark on bottom of amber bottle created by Illinois Glass Organization. By the way, there ARE authentic purple glass Hemingray No. 9 insulators, but they date from the late 1890s or pretty early 1900s and do not have the same lettering arrangement as your comparatively contemporary quantity 9. All authentic purple Hemingray No. 9s have the embossing “HEMINGRAY / NO. 9” on the front and “P