It's promoting her 1940 RKO film "Vigil In The Night"...but while it may resemble a lobby card, it isn't. Rather it's something called a glass slide, and it's all of 3 1/4 x 4 inches. That may not seem like much, but it had a big impact. As the seller, Marty Davis of Arizona, explains:
"It was created to be projected on the movie theatre screen before the film was released, to promote the 'coming attraction.' The fragility of glass slides make those that have survived (especially those in excellent condition) very rare pieces of film history. Surviving glass slides are much rarer than the paper poster memorabilia from the same film."
At the bottom, you can see part of an inscription, "State, Mon.-Tue., also short subjects." (In those days, neighborhood houses often changed the program two or three times a week, unless the film was a special attraction or an unusually popular hit.)
The seller adds that glass slides "were first made during the early 1910s. They were used to show 'previews' of coming attractions, and were projected before the films began, and between films of double feature presentations. They continued to be made through the early 1950s, but were used much less frequently after movie trailers began to be shown in the 1930s. Glass slides continued to be produced and used in New Zealand through the 1980s."
Unlike lobby cards, whose contents they sometimes duplicated, glass slides were rarely of interest to people other than the theater manager or operator -- so relatively few people are aware the form ever existed. Moreover, most were disposed of after the production made its run. Not until the 1970s, by which time relatively few had survived, were they perceived as collectibles.
What can one do with glass slides today? Davis says, "Glass slides can be projected on walls or screens with vintage projectors, as well as projectors currently available. Some people have made illuminated display cases for their slides."
If this piques your interest, check out the slide at its eBay site, http://cgi.ebay.com/CAROLE-LOMBARD-orig-1940-Glass-Slide-VIGIL-IN-THE-NIGHT_W0QQitemZ170165469924QQihZ007QQcategoryZ14278QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
One wonders how many glass slides survive from other Lombard films. In the meantime, here are two more promotional items from "Vigil":