The largest of the three sizes that work in the Honeywell Tilt-a-Mite and the
Argus C3 gun. We include the 35mm film can and a roll of 120 film for size
comparison. Note the purchase price on the upper right of the box (circa 1965).
Depending on maker these were called #5 or #25 or 'Press 25' as seen here.
The 'Blue Dot' is a spot of chemical in the interior of the bulb that turns
pink if moisture gets into the bulb, warning of possible hazard or failure.