Question: what is red jewel for re2?
Answer: In the art room by solving the commemorative photo puzzle you get a scepter. Examining it gives a red jewel. In the interrogation room you will find a box, combining it with the red jewel opens the box and gives a S.T.A.R.S badge. S.T.A.R.S badge can be used to access the armoury in the S.T.A.R.S office.