The tintype, or ferrotype, was an inexpensive form of photography aimed at the masses. It was introduced in the 1850s and became popular during the 1860s to 1880s. It survived at beaches and other resorts, though, well into the early-1900s.  The photographs, actually captured on iron plates, not tin, were very durable, and thus well-suited for being sent through the mail. Many Civil War soldiers had their likenesses captured in "photograph and ferrotype galleries" and sent the image back to their loved ones waiting at home.

An outdoor family portrait made with a poor quality lens - note the curvature around the outside

A very unusual set of four images - see the detail below - is the man holding a bag of peanuts or something???

Another uncommon gem image - most were only of a single subject's head and shoulders

A full-plate image (6.5" x 8.5") of a farmhouse

Tintype of a young Salvation Army officer, 
circa 1870s