Please see this photo:
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fitting is in the kitchen; there are two of them about a yard apart, on the wall that separates the kitchen from the dining room, about a foot from the floor.The front face of the cap is stamped with the letters "GF" and "1/2".
The question is, what service might these be connected to?
The house is late-60s open-plan, and there is a separate gas fitting for the cooker space. The kitchen fittings are original.
TIA for any pointers.