Yes they are a jig for fitting an old "Ascot" type sink water heater top gas bottom water if I recall correctly.
They were common in the 60's on new builds lots of council places had them as standard.
Some are live, some just run down to under the work surface for a customer to get the gasfitter to connect out of sight and so avoid surface run pipes, but best to assume they are both live.
Proper course would be to get a gas safety engineer to check for you.
Not really having them cut off and removing the jig is the only way to get it flush.
The jig in the wall is quite bulky about 6" X 3" galvanized and with two elbows built in to it normally connected in iron pipe.
Maybe you can fit something like a small unit or a clock over it but beware of the pipework in the wall, when fixing.
It could be as cooker or a gas fridge point, again standard at the time.
Another possibility is that often the gas was connected but the water only run down for the water to be connected if required.
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