The Doctor's Knife is a truly unique pattern. Featuring a "pill crusher" bolster and usually a spear and spatula blade. Though some are double bladed with a spear and pen blades; and a single spear blade was made as well. The Doctor's Knife was most recently featured in 2018 as Case's Vault release pattern.
Pictured: Buffalo Doctor's Knife
The Doctor's Knife is assembled on a Case pattern #85. Only one other knife was assembled on this pattern, the Sleeve-Board Style Whittler, which was produced before 1915.
The Doctor's Knife is traditionally 3 5/8 inches closed, though a Baby Doc was also produced that measured 2 3/4 inches closed.
Introduced prior to the 1940s, Case stopped producing the pattern around the mid 1970s. However, there were a few special production runs in the 1980s and 90s. Eventually, the pattern made a full return to production in 2001 before being retired again by 2018.
As you may have guessed, the knives were traditionally used by doctors making house calls. It was viewed as a sort of doctor's multitool. The long spear blade could act as a backup or emergency scalpel or to cut pills. The spatula blade could aid in mixing salves/medicines or as a tongue depressor. And the flatten bolster (aka pill crusher bolster) was used to grind pills and other ingredients into powders.