The soldier, Charles Jeffries, sent the card from Limburg an der Lahn on April 30, 1918 to let his family in Westcliff-on-Sea, Essex, know he had been taken prisoner.
His 78-year-old granddaughter, Pat Nicholls of Shepreth, Cambridgeshire, had the card in a file of family memorabilia.
She is trying to find out more about the role her grandfather played in the war, 'BBC News' reported.
The card gives Jeffries' regiment as the Royal Naval Division but does not indicate whether he was wounded.
Nicholls has had the postcard in a file of family memorabilia.
The card, which Nicholls has handed over to historians in Shepreth, is printed in a mixture of German and English and headed "I am a prisoner of war in Germany."
Nicholls said Jeffries died of lung cancer in 1953 while she was a teenager.
"I remember him well. I wish I'd asked him about the war. But people didn't talk about it," she said.
"He was a waterworks inspector and worked for the Southend Waterworks Company.
You’ve reached your limit of {{free_limit}} free articles this month.
Subscribe now for unlimited access.
Already subscribed? Log in
Subscribe to read the full story →
Smart Quarterly
₹900
3 Months
₹300/Month
Smart Essential
₹2,700
1 Year
₹225/Month
Super Saver
₹3,900
2 Years
₹162/Month
Renews automatically, cancel anytime
Here’s what’s included in our digital subscription plans
Exclusive premium stories online
Over 30 premium stories daily, handpicked by our editors


Complimentary Access to The New York Times
News, Games, Cooking, Audio, Wirecutter & The Athletic
Business Standard Epaper
Digital replica of our daily newspaper — with options to read, save, and share


Curated Newsletters
Insights on markets, finance, politics, tech, and more delivered to your inbox
Market Analysis & Investment Insights
In-depth market analysis & insights with access to The Smart Investor


Archives
Repository of articles and publications dating back to 1997
Ad-free Reading
Uninterrupted reading experience with no advertisements


Seamless Access Across All Devices
Access Business Standard across devices — mobile, tablet, or PC, via web or app
