BSA, better known later for motor-bikes, issued valves in 1926 under the name BSA Standard. Standard was the brand name of STC at the time who were in turn a subsidiary of the American Western Electric company.
Thanks to John Shidler for the images.
The identification lettering.
The Peanut base connections. The valve holder is of the locking bayonet type.
The main logo with BSA Standard and the Type designation.
In this image the cylindrical anode and helical grid can be seen. See alsoG125A.
The thin glass tube envelope is 16 mm in diameter, and including the Peanut base pins is 65 mm tall.
References: 1043. Type G125A was first introduced in 1925.