Geoffrey was last seen near to his home on Arbroath Street in Droylsden at around 2pm on Monday 24 July.
He is white, of slim build, around 5ft 6in tall with short grey hair and a white beard.
He speaks with a Manchester accent and was last seen wearing a black and grey raincoat with orange stripes on the sleeves, brown/beige trousers, a navy pullover and brown Timberland boots. He was also seen wearing a soft, green corduroy cap.
Detective Inspector Julie Maxwell of GMP’s Tameside Borough, said: “Geoffrey has been missing for four days now and as the days and hours go on, our concern for him grows.
“I want anyone who has seen him to get in touch with us as soon as you can and I want you to be mindful that he may need medical attention due to the amount of time he’s been away from home and the inclement weather we have recently experienced.
“Four days is a long time to be away from your family and our only hope is that we can reunite Geoffrey with his loved ones as soon as we possibly can.”
If you see Geoffrey, please contact 101 quoting MP/16/0097208 or the independent charity Crimestoppers, anonymously, on 0800 555 111.