Ah that explains it. It was not taken up on a pontil rod but on a blowpipe. Here is a photo of two "jasmin vases" (not lilac, how dare I) from around 1860 made in Belgium (Louis Zoude) and/ or in France (Nancy region). The one on the right has a similar opacity obtained by zinc oxide which is 'struck' to opaque in the oven. There seem to be quite a number of models, but yours is the first one I see which is totally smooth. Colours known are Cobalt, cobalt to opaque light blue, and white. These vases even if they count as early pressed glass have pontil marks because taking glass items out of the mould was quite difficult, and often a pontil or blowpipe was used to remove the finished article.
Perhaps someone else will have something to say. Pamela, are you there?