A marrow scoop is a spoon used to remove marrow from bone. This type of spoon is long and narrow which allows you to more easily dig into the interior of a bone to extract the marrow. These spoons were mostly made of silver.
Marrow scoops were introduced around the time of the Queen Anne era (r. 1702-1714). They were mainly used by the upper-class as marrow was an expensive food to eat on a regular basis.
In today's times marrow scoops are hardly used because eating marrow has gone out of favor. However these types of scoops are now occasionally used for other purposes. For example, they are sometimes used as drink stirrers.
Value
Antique silver marrow scoops can sell for hundreds of dollars. Some of the later versions are silver plated and thus not as valuable.
Sources:
The Book of Old Silver