An amputee was beaten with his own walking stick after four men attacked him in a park in Smethwick.
The 54-year-old man, who has one leg, escaped with minor injuries after being subjected to the "sickening" assault in Victoria Park on 3 September.
Four men approached the victim at about 8.30pm, punched him in the face, knocking off his glasses, and restrained him while his pockets were searched.
When the victim began to struggle, one of the men grabbed his walking stick and began to attack him with it as another broke his neck chain.
Detective Constable Pete Miller, from Sandwell CID, said: "This was a nasty attack on a vulnerable man - the reason he had a walking stick is because he is an amputee and only has one leg, which makes this incident all the more dreadful.
"He escaped with only minor injuries, mainly pain to his leg and nose, but the mental scars will take some time to heal."
Witnesses or anyone with information about the offence should call Sandwell CID on 101 or the Crimestoppers service anonymously on 0800 555 111.