Thousands of Dutch residents have been rummaging through their trashcans in a diamond rush after a jeweler’s anniversary mailing was largely ignored as junk mail, the BBC reports.

Jeweler Johan de Boer in the eastern Dutch town of Apeldoorn, sent real and fake diamonds to 4,000 of his clients—telling them they could keep the real ones, the BBC reports. He couldn’t sleep last night after his promotional effort backfired.

Amsterdam is famous for its diamond-cutting industry but it is most unusual for clients to receive real stones as a Christmas gifts from their retailers. So most of De Boer’s clients didn’t take him seriously when he mailed them stones to mark the 10th anniversary of his jewelry store.

It cost him 48,000 euros ($59,549) to send out 200 envelopes containing a small diamond along with some zirconia.

The letters asked the clients to bring the stone into the shop—if it was a real diamond, they could keep it.

Only 35 people turned up, the BBC reports. After calling some of his clients, De Boer realized most had thrown the envelopes away without even opening them.

He reportedly told a newspaper he had been very naive and regretted it.

JCK