Eisler's Patent float

I have just retrieved from my fathers shed (after some 20 years), some boxes of items which had belonged to my grandmother and which I kept when she passed away because I thought they were interesting. I am having all sorts of trouble finding out more about them and, having just discovered this site, am hoping that someone can enlighten me. The item pictured is 15cm high and 10.5cm wide. It has "Eisler's Patent" embossed in the glass, but no other text or insignia. The glass is clear with one horizontal and one vertical line running through the middle, both which end at the bottom of the neck. The neck is at a slight angle and is sealed at the top by glass. There are lots of air bubbles in the glass itself. All I have been able to discover is that it is probably a toilet float. After some research I believe that the words may relate to a patent by one Charles Eisler on the technique of glass sealing bottles (instead of using a stopper). These floats were apparently quite common before WWII and were then replaced with cheaper plastic or metal versions. I have only been able to find one other the same as mine.