From DoomWiki.org

extras.wad is a file included in the 2019 re-issue of Doom and Doom II, containing additional resources used by these ports, namely the skull, health bonus, and interrogation mark icons used for the automap statistics, the weapon sprites shown on the weapon selector, crosshair graphics, and a DSSECRET sound lump.

It is 64,779 bytes in size, and contains 24 lumps.

Hash type Hash code
MD5 0c7caf25ad1584721ff5ecc38dec97a0
SHA-1 55a6a95c99d7fe7b9501d34b0afecd3252a629e1
CRC-32 8068229f

Before the September 3 update that added the crosshair, it was 64,587 bytes in size, and contained 22 lumps.

Hash type Hash code
MD5 38e1bb6cdd1e4227eef13d22f6e35209
SHA-1 0f2a7139b640e19a08f384562f907cb0734b0512
CRC-32 82bccddc