The half and half acid stoneware bottle from the Manhattan Rubber Mfg. Co. in Passaic N.J. would date to around 1900-1920 I would think. It was one part of two ingredients needed to repair early rubber tires. The other ingredient being a "rubber" cement. Repairs were done by using the acid versus ordinary heat vulcanizing. Ingredients would come in containers ranging from 1/2 pint to a gallon.
If that was on the top layer I can only imagine what you will find once you start digging!