A photographic process in which the negative image is produced on a thin, coated plate of iron (there is actually no tin involved). Tintypes first appeared in 1854 and enjoyed their widest use during the 1860s and 1870s. Video here.

Photistoric_36455v_0006Edwin Chamberlain of Company G, 11th New Hampshire Infantry, in sergeant’s uniform with guitar. Tintype. 1861-65.