I don't know the exact size of the bulb but it is small, like a flash light bulb maybe? It also has a place for a name or address tag.
This is NOS and appears to have never been used. The blue glass does have a small crack. The brass has a deep beautiful patina tone.
I have several of these if you need more then one. Approximate Measurements The piece is 6" tall and is 2 1/2" x 2 1/4 wide.1.6# Markings Pat Apld For, The Illuminated Push Button Condition Good condition with a beautiful deep patina tone. The brass has a nice patina. The glass lens has a small crack. See description above for further info on the condition. Vintage Brass Door Bell Lighted Cover w Colored Glass > Lens Antique 8644. The piece is 6" tall and is 2 1/2" x 2 1/4 wide. Pat Apld For, The Illuminated Push Button. Good condition with a beautiful deep patina tone. Auctiva Offers Free Image Hosting and Editing. The item "Vintage Brass Door Bell Lighted Cover w Colored Glass Lens Antique 8644" is in sale since Monday, September 4, 2017. This item is in the category "Antiques\Architectural & Garden\Hardware\Door Bells & Knockers".
The seller is "*miliki*" and is located in Red Oak, Iowa. This item can be shipped worldwide.