From about 1964.
It is marked in Dymo tape "BRISTOL - DURHAM" if that label is original then the aftermath of the Great Train Robbery comes to mind when railway GPO Travelling Post Offices were fitted with Police frequency radiotelephones to call in at the entry into each county and out of each county as well as probably when stopped at signals. Callsigns used were such as QUEBEC and as each train journey went from specific town to town a specific crystalled Vanguard would be required for the counties that it's railway track passed through. If this is true then does anyone remember these in use?
Comments please to Dave Hicks G8EPR at the Pye Museum