Of interest, each of the three apertures on the second level pictured contains two spirit vials. Most levels only contain one.
Parry and Bott were located on Baltimore Road, Hampstead, Birmingham and specialized in spirit levels. They may have introduced the line level, the small level you hang off of a string. They were still in business in the 1960's but have long since departed for toolmaker's Valhalla.
|1951. Source: Grace's Guide to British Industry|