Vintage glass lantern slide is in very good condition
 
Measures 4 x 3.25 inches
 
Marked: “Steel Works, Hangyang” 

Image is clear and sharp (looks better than my photo).
 
This photo was taken for the Methodist Episcopal church (U.S. missionary religious work) around or before 1920 in China.  

We will have several for sale at eBay and some are marked Methodist Episcopal church and  “foreign missions.”

Glass lantern slides allowed the image (photograph) to be projected on a large screen for an audience to see. 
They consist of a black-and-white photographic emulsion on a primary glass plate, meticulously hand-painted with transparent dyes for color, and topped with a second piece of glass to protect the image, with the edges bound by black paper tape. 
Projected using "magic lanterns", they were the 19th- and early 20th-century equivalent of modern slide shows or cinema, used for widespread public entertainment, education, and lectures.