This is part of Strathearn's Aurora series of pwts comprising these minatures, medium to small ones, large and a jumbo series. I've not found a formal description nor why this series is called Aurora. It appears made by first using a gather of clear molten glass that is then coated with the same types of glass that Strathearn used as a ground for many of their pwts but first rolled in a tray of broken cane chips and bit pieces and then covered with another gather of clear glass.. Columns of bubbles are then introduced forming the divisions or slices. On these P26 minatures the bubble columns are three to four bubbles high depending on the size of the minature with the final or top bubble forming a cap at the top of the Aurora pwt. These minatures range in size from about 1.3" wide to about 2.2". Colors are stated as being in Grey, Red, Green, Blue and Black but I've also found one in a multi-color range. Production quanities are unknown at this time and for now produced from 1965 to 1979.