This is a compass and all the aircrew had one in the top button of their tunic. (This compass is the size of an ordinary tunic button and has luminous blobs to mark the settings).
Do those blobs glow in the dark?
Yes it is luminous and potentially is highly toxic. Many of the girls used to lick them but later they suffered from serious health problems. I have here a long service brooch that I got after serving 30 years with De Havilland's. When they first wanted to move to Hatfield from Stag Lane Lord Salisbury tried to block them but he couldn't because the bypass was the edge of his land. He wanted to keep Hatfield so that more food could be grown to feed local people but when De Havilland's did arrive then the town of Hatfield really changed because it was developed according to the needs of De Havilland's.
All the old milestones have got Hatfield on and that was something Lord Salisbury had done.
Hatfield was known as Bishops Hatfield in the time of Henry VIII.