That would be a stacker jug.
Jugs were made with rounded tops at one time. Like the local Crawford county Georgia jugs. They had to be fired in a single layer. That took a lot of wood. So potters started using a jig to turn them in uniform sizes. And if you notice where the cone top met the sides there is a ledge or lip. A pre fired collar was placed on that lip, extending above the cone, and another jug was placed on top. Then they could be stacked up multiple jugs high. Many more fit in the kiln at one time. Not as personal as the old green ones, with round tops and actually hand made glazes that varied in colors too, nor as valuable, but I still like them. I kept two stackers and had to sell the high end ones. Ah well, at least I paid the bills. Look for a stamp bottom, sides or handle, some had them. Some of them can bring good money, and even broken handles foe repairs sell. The glaze looks like Albany slip which was a commercial glaze. Pottery eventually gave way to machine made glass. Pottery was a cheap commodity due to Georgia and other states abundant clay deposits. A good read is Brothers in Clay, a history of southern potters from the 1800s.
A note: the bootleggers used them during prohibition ,and revenue agents traced the potters marks back to the potters to go after the moonshiners. So pottery marks disappeared, and soon the unmarked, then stackers were the norm. Then came glass.