Role in series
In the film, they are used as a means of hinting at the secret unnamed organization (i.e. V.F.D.), and of Uncle Monty's membership, and the Baudelaires receive a spyglass from their parents as a "rite of passage" according to Lemony Snicket.
In the TV series, the spyglasses return and are given a more explicit purpose, to decode secret messages between V.F.D. members and keep a lookout in general. It is also shown that, with specific arrangements of the code dials, the spyglasses can function as a flashlight, code-breaker, and a fire-starter. The Baudelaires recover one half of a spyglass from their destroyed home, and they encounter the Quagmire triplets who possess the other half of a complete spyglass. It is also revealed that these versions of the spyglasses are capable of producing a beam of concentrated heat. This is likely the cause of the Baudelaire and Quagmire Fires, but the identity of by whom used it is still unknown.
In the novels, a spyglass used by V.F.D. is only briefly mentioned in The Slippery Slope.
The spyglasses in the film are seemingly made of solid brass, but in the TV series, the spyglasses seem to be made of wood with rotating rings on one half, seemingly used for certain settings or different codes, and navigational compasses or gauges on the other half. The draw-tubes that pull out are made of solid brass with some rotating wheels and numbers, and the top of the spyglass has a cap bearing the V.F.D. insignia. Though the creator of the spyglasses is unknown, a common candidate would probably be Gustav Sebald, as he is known for creating the Sebald Code, which was featured in the film Zombies In The Snow, which Uncle Monty used a spyglass to decode a message hidden within the subtitles of the movie in the TV series.
Some known owners of V.F.D. spyglasses are:
- Klaus Baudelaire (technically only owns half of a spyglass)
- Bertrand and Beatrice Baudelaire
- Isadora Quagmire (technically only owns half of a spyglass)
- Mr. Quagmire and Mrs. Quagmire
- Montgomery Montgomery
- Lemony Snicket
- Count Olaf
- Gustav Sebald
- Larry-your- Waiter
- Quigley Quagmire
- Kit Snicket
Some suspected owners:
- Esmé Squalor
- Aunt Josephine (maybe even for bad purposes) 
- The Man with a beard but no hair
- The Woman with hair but no beard
The Starting of the Quagmire Fire
In the TV series, in the starting of the Quagmire Fire scene in The Miserable Mill: Part Two, a person is seen in their car behind a newspaper wearing a very fashionable dress of monochrome. On the dashboard of the car is a spyglass. Due to the very fashionable dress that the person is wearing, the person is commonly suspected to be Esmé Squalor this is however not confirmed due to the fact that the disguise worn by the arsonist is found in all VFD disguise kits. (see VFD Disguise Training). It is also speculated to be Count Olaf.
It is possible that the spyglass shot the laser that started the fire. Due to the convergence of light, it could very well be possible for a laser to be shot through the spyglass to make a fire starting beam. In The Incomplete History of Secret Organizations, there is a passage named "Starting Fires: Using The Sun And a Spyglass by Josephine Anwhistle" It is strange that she would even write a passage like this as she was part of the Fire-Fighting Side.