ᐅ Backfilling, 3/4 inch or 1/2 inch?

Hello, a quick question about my house:

A few years ago it was built, and in the basement, building plugs were inserted into two water pipes. Now I finally want to install a utility sink in the basement and replace the plug with a faucet.

This might be a silly question, but... Is the pipe size 1/2 inch or 3/4 inch? I’m assuming it’s 3/4 inch, but I’m not sure. Using a caliper, the plug measures about 22 mm (0.87 inches) internally (front side) and 31 mm (1.22 inches) externally (I don’t remember the exact values anymore). I’m guessing it’s 1/2 inch, not 3/4 inch. Is that correct?

Can anyone advise?

A photo with the recorded measured values would help to answer. Also, please clarify whether you mean thick-walled pipe or thin-walled precision pipe.

PS, building stops for fittings are usually 1/2" (1.27 cm). However, they are also available in other sizes.

Right, two photos attached. This was a quick shot taken last night because I wanted to make some progress :/

1/2"
and now I still have to reach the minimum word count for responses 😉

Thank you for the prompt support!