The porcelain insulator fragment was recovered during the excavations on the exterior of the Long Barrack.
There are often two types of insulators that would have been used during the mid-1800s to the very early 1900s: glass or ceramic. The ceramic varieties were often white porcelain, although brown glazed insulators and bisque insulators can be found as well.
This smaller variety found outside the Long Barrack likely conducted electricity. A nail would have been present through the hole (it appears to be a rusted fragment currently) and the electrical wire would have been wrapped around the groove (noticeable if the artifact was complete).