"Demonstrators were originally not for sale. They were furnished by the manufacturers, and used as sales tools to show dealers, salesmen, and customers how a pen or pencil was constructed and how it functioned, and to instruct repairmen". "Although a few purists argue that modern transparent pens aren't really demonstrators, that is a pointless effort to impose the standards of one era on another. Modern transparent pens are sold as demonstrators, after all, and they undoubtedly demonstrate"  (by David Nishimura).