Panorama slide: Small ('toy') format -- 2.5 inch
Sample image of this type of slide – slide shown is slide 1-3 of The Swiss Family Robinson: [2.5 inch size] (story: Theobald & Co., 4 slides, in/before 1893)
Ilfracombe Museum collection – reproduced by permission. Digital image © 2019 Ilfracombe Museum.