I realize that this can be a controversial subject however; during the Victorian era many exotic materials were incorporated into fine tools from the mid-19th century onward. Most of these materials (Ivory, Cape Buffalo horn, Brazilian Rosewood, Cocobolo, Gabon Ebony, etc.) are not traded on the world market today. My intent here is to present things as they were.
Ivory folding rules were by-and-large gifts and presentation pieces. The trim was German Silver as opposed to the general brass trimmings. They were considered a good choice for a retiring tradespersons.
The ad above depicts a Stanley No 40 which was “enclosed in a neat leather case”. The No 40 shown in the picture above came with its “neat leather case” and is the only one I have ever seen with said case. It is also exceptional due to the whiteness of the ivory and that it has all of its alignment pins.