Vintage Flash Bulb "1815" (ANSI code ?), Unknown Manufacturer

Description

From what research I've done on this bulb, it is of the 1920s-1930s vintage and, obviously, never used.
This flash bulb belonged to a late lighting engineer friend who collected light bulbs
.
The only labeling I can find is inside, a black dot with "1815" under it.  This may be an ANSI code number.  ANSI, I've learned is the
American National Standards Institute, an organization that
develops standards for a wide range of commercial products and
in lighting, assigns codes that have a particular relevance to common types of light bulbs, though they are less and less common in modern lighting uses.
The bulb measures 6" from tip to top and 3" in diameter.