Alcoholic Simon Emeny found a knuckle-duster in the gutter after buying cans of beer in London Road, Grantham.
Kate Macmillan, defending, said Emeny walked only a few yards with the knuckle-duster before he was stopped by police and arrested.
She said: “He came out of the shop and saw the item in the gutter. He picked it up, knew what it was, and put it on, very stupidly.
“He showed it to a friend who said ‘quick, put it back’. He panicked and could not get it off as he has big hands and his fingers had swollen up. He walked only 10 yards before he was stopped by the police and arrested.”
Mrs Macmillan said Emeny, who admitted possession of an offensive weapon, is a vulnerable man who suffers from alcoholism, schizophrenia and Parkinson’s disease.
Magistrates adjourned the case for a pre-sentence report. Emeny, of Hillside Road, Woolsthorpe, must return to court on October 1 to be sentenced.