Unusual Aqua Glass Onion Bottle

Aqua glass onion bottle with circular rough pontil. At first i thought this bottle was German but i cannot be exact in its attribution as its unlike anything i have seen before. The thick rim is not typical of anything from abroad with many bottles having a thin wall and the thin string rim is very English in style. Regardless of where it comes from the form is great and is very unusual in every respect. No question it is 18th century and i would pitch it C1750. Height 6 inches, width 5 inches. There is one 1/2 inch impact crack  towards the base area and a good amount of wear around the body and base. No internal staining or other issues. Mid 18th century.