Thanks for posting. I especially like the photo of the bottle as found, sitting in the mud.
The keystone-K mark on the base is for Knox Glass Bottle Co. of Knox, PA. According to Glass Makers and Their Marks, this mark was used from 1924 to 1968. On first impression without seeing the mark, I would have said mid-20th century...
No real value here but keep looking - great bottles turn up all the time. Rivers and ponds have been on the minds of bottle collectors in recent years, and thus the source of some great discoveries.
