Antique German Pottery Crock

I have recently bought this pottery crock at an auction for $5.00. I have been researching what this crock may be. I have seen on different websites that it may be from the 1800's and that it may be a mineral water crock although a recent appraisal stated that it is a wine crock worth about $48.00. I wanted to get different appraisals to see what it actually is and how much it's worth. I have seen on ebay similar crocks listed at almost $300.00. One listing stated that in May 2012 a crock like this sold for over $300.00. I have seen wine crocks that resemble this one but still look different. The wine crock did not have the 3 thread markings at the top  of the bottle and they looked quite smooth in appearance. This crock looks as if it was hand made throwing it on a potter's wheel and hand forming it because you see imperfections such as finger marks and uneveness in the formation like it was smoothed by hand. It looks as though some sort of bands were used under the clay especially around the handle part. It has no chips or cracks, just the imperfections already stated that you would get with something hand formed. There is a stamp on the front as seen in the photo with words "J. Friedrich Grosskarben B/Frankfurt M and a round marking with lettering I can'r make out. A number 9 on the back under the handle. A felt piece has been placed on the bottom. It stands 11-3/4" and diameter of 3-1/2". There used to be a cork. It's fallen inside. You can hear it rattling. It's brown in color.