Space: 1999 (1975) Model Probe from "The Last Sunset"
This is an original model probe, created by Martin Bower, from the "Space: 1999" episode "The Last Sunset". It measures 5cm, plus 3cm for the antennas. It originated from the collection of Brian Johnson, special effects director of the series.
You can find more information on the episode in the Catacombs.