The incident happened Friday afternoon at Matto on Seventh Avenue in Chelsea.
Investigators say the police captain was a customer at the restaurant and saw the thieves grab the jar.
The captain followed them outside and began tussling with them.Eventually the thieves ran away.
They are still on the loose.
Anyone with information about the suspect is asked to call the NYPD's Crime Stoppers Hotline at 1-800-577-TIPS (8477) or for Spanish, 1-888-57-PISTA (74782).
Tips can also be submitted by visiting the CrimeStoppers website or Twitter @NYPDTips.
All calls are kept confidential.
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