Old German Bottle ~ What is it?

I've had this bottle for years, I've never known what it's original use was. It measures 3 1/2" high and the bottom is 2" diameter. The bottom is an amber color and it's marked Germany on the bottom. The cap screws on and is metal with what I think was rubber (it's hard now).

Does anyone know what it is? I love the shape!

Thanks.