[Careynew]

Hello all. My name is carey and I have just joined this forum. I have had a love of trains since childhood especially steam. My Father in law passed away recently and I am helping my partner to sort out his effects. we came across an item that we are not sure about and would be gratefull for any information from members.
It is a small black box with a label on the side saying signal angle setter GWR. Inside the box is a round metal(steel?) instrument with a glass panel with a gauge two rows of numbers, the top one from 0 to 90 from the centre left and right and the bottom one from 5 to 85 from the centre left and right. There are no stamps or markings on it so we are not sure if it is what it says on the box.
Any help would be appreciated,
Many thanks
Carey