A teenager who was arrested following the incident where West Brom midfielder Chris Brunt was struck in the face by a coin will face no further action.
Thames Valley Police made an arrest in February after Northern Ireland international Brunt, 31, suffered a cut under his left eye when he approached the stand housing Baggies supporters following a 3-1 loss to Reading in the FA Cup.
The force have now said a 17-year-old has been given a caution in relation to the matter at the Madejski Stadium.
In a statement published on BBC Sport's website, a spokesperson for Thames Valley Police stated: "A 17-year-old boy has been given a youth caution for using threatening or abusive words or behaviour or disorderly behaviour, likely to cause harassment, alarm or distress.
"No further action was taken in relation to throwing a missile onto a football playing area.''
The Football Association had also launched an investigation into the incident against Brunt, who called the act "absolutely disgusting''.