The Duplex started out around 1909 as a double extension version of the Ruby Reflex. From about 1910 the Duplex was advertised as a model in its own right and differed from the Ruby.

Originally available in 3 ¼" x 4 ¼", 5" x 4" or postcard and 6 ½" x 4 ¾", the combined 3 ½" x 2 ½" or 3 ¼" x 3 ¼" was added in 1911 and called the Bijou. A revolving back was fitted from 1910 in place of the reversing back. At the same time a mirror lock prevented movement of the mirror when the hood was closed. The 5" x 4"/postcard size was available without the revolving back option, it would then have a fixed back for horizontal work, making it cheaper and more compact.

Some time prior to 1914 models for 9 x 12 cm and 7" x 5" were added. Continental equivalents were available for the other English sizes. Some, probably late, examples have lazy tong supports between the body and the front standard.