The pricetags on the postcards at the Smithsonian museums are welcome anachronisms, still holding their own against inflation at 10 cents apiece, three for a quarter. Those at the National Gallery of Art are reproductions of works in the gallery's collections, and so lend themselves as a truly artful, and cheaper, way to send holiday greetings (10 cents as opposed to 15). Greeting, note and post cards of art collections are also available at the Hirshhorn Museum, National Collection of Fine Arts and National Portrait Gallery. For anyone with decorative gifts in mind, striking posters designed to announce art exhibitions at various museums, along with other frameable prints, are available at the National Gallery, Hirshhorn and NCFA. The National Gallery also solves the where-quickly-to-find-a-frame-to-fit dilemma with an amazing selection of very reasonably priced framed reproductions ($9.95 to $50). All four museums offer paperback and hardback books as well as special exhibition catalogues. Some of the National Gallery's collections have inspired jewelry reproductions ($6.50 to $15), while the Hirshhorn and NCFA sell abstract-design pendants and bracelets, and numberless Chromachron timepieces ( $45 to $150) that use bands of color to indicate the hour.