Bowers writes extensively on the coin world and has 37 other works listed at Amazon.com. No informative review present so I am guessing that 'encased' represents authenticated material that is often 'encased' after authentication. aj.
...spanning nearly a century of examples dating from salt prints to picture postcards. The over three hundred illustrations are accompanied not only with value and dating guidelines, but also historical background on the development of the various card types. Included are family portraits, famous personalities, the frontier West, Civil War scenes, theatrical cards, oddities, foreign landscapes, and studio novelties. In fact, the profusely illustrated text is a documentary of a bygone era.
"..shows collectors how to invest in the growing foreign stamp market, too, featuring in-depth descriptions of more than 5,000 foreign errors prices at $200 or less. 500+ photos.."