Thieves wrenched a wedding ring from the finger of an 82-year-old man during a raid on his home.
The gang of burglars threatened Subramaniam Vijayaratnam, ripping a telephone cord from the wall when he tried to call police.
The three men, described as white, also tore a gold chain from his neck before ransacking the property and making off with a "large amount of jewellery".
Thames Valley Police is appealing for witnesses to the crime on 4 April.
Mr Vijayaratnam was alone in the house in Bletchley, Buckinghamshire, when he noticed the men in the rear of his property at about 20:00 BST, officers said.
"I cannot imagine how frightened the victim must have been as the three offenders ransacked his home for about 20 minutes, during which time they stole a gold chain from his neck and his wedding ring from his finger," PC Christopher Bigg said.
"Thankfully, the victim was not injured during the incident but he has lost a number of items of jewellery that have great sentimental value."
"Physically, fortunately, I've not been affected," Mr Vijayaratnam said.
"But I think that mentally, well, you can't describe it. I never thought it would happen to me."
Detectives are looking for the three men who they believe left the property via Cornwall Grove, where a getaway vehicle may have been parked.