A variation on the "Arranged Object" mounts, Exhibition slides were often considered to be the pinnacle of the commercial mounters art, considering the degree of difficulty in their preparation. Combining various objects, often many 100s (or 1000s!) of individual butterfly or insect scales, diatoms, spicules, etc.; each piece was individually selected and assembled to create pictures or complex geometric arrangements. Many of these amazing "picture" slides using butterfly scales were made in the last quarter of the 19th Century by H. (Harold) Dalton, which were then often factored through W. Watson & Sons of London, and carry their secondary labels. 

The image immediately below, is composed of diatoms, butterfly scales, and plates and anchors of Synapta. It is a beautiful example of the geometric variety of exhibition mount.

Above, an Exhibition Mount of Arranged Diatoms by Watson & Sons, London, c. 1885; and below, two Exhibition or Picture Mounts made using butterfly and insect wing scales. Immediately below, "Flowers, Grasses, Ferns, Insects, and Birds", and far bottom image "Bouquet with Insects, Etc.", both by W. Watson & Sons, London, c. 1880s. All three imaged using combinations of Darkfield and or Reflected lighting techniques.

Exhibition Rosette of Arranged Diatoms by E. Thum, c. 1880s