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 on to a football playing area."
The Football Association had also launched an investigation into the incident against Brunt, who called the act "absolutely disgusting".
Press Association Sport have contacted Thames Valley Police regarding the matter.