This is Strathearn's medium to small P27 Aurora weight. There's no formal description on 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 type of glass that Strathearn used as a ground for many of their pwts but first rolled in a bed of broken cane chips and pieces. Columns of bubbles are then introduced forming the divisions or ribs and then coated with another gather of clear glass. On these P27's the bubble columns are five bubbles high with the final or top bubble forming a cap at the top of the Aurora pwt. These range in size from under 2.5" for the small ones to 2.5" plus for the mediums but less than 2.7" at which the large Aurora starts. Made in colors of Grey, Red, Green, Blue and Black. I've found no other colors yet. Production quanities are unknown at this time and for now assumed from around 1965 to 1979.