Glass Ship in a Bottle

This piece of glass absolutely amazed me because it is beautifully detailed and I love ships of old. This measures 10" x 3", and has a little inverted pontil in the middle underneath the ship. I cannot even imagine how this was done. Do not know the manufacturer, this came in a box as though it were mass produced for a dime store. I acquired this so many years ago that I cannot remember where I put the box. If anyone has any additional info, I would love to know more.