Two brothers have been jailed for violently robbing two security men delivering cash to post offices.
Shani and Simeon Ebanks stole £47,000 in the Birmingham attacks that happened eight days apart in September 2016.
They were foiled when police found an abandoned cash box with a trail of purple dye that matched traces found in their getaway cars.
Simeon was sentenced to 13 years and his brother received 12 after they were found guilty of robbery.
Shani, 25, of Maria Street, West Bromwich, and Simeon, 27, of Clinton Street, Winson Green, Birmingham, first stole from a delivery man at Summerfield Post Office in Winson Green on 14 September.
The brothers threatened him with a knife and stole £26,000 cash in a security box.
Eight days later the pair robbed another cash driver of a security box containing £21,000 from the Kingstanding Circle Post Office.
They fled in a stolen blue Ford Focus, later changing to a black Peugeot 206.
When police were called to the abandoned Ford Focus, they found a trail of purple security dye leading to a cash box and a plastic bag containing stamps.
Shani Ebanks' black Peugeot 206 was found shortly after parked outside his brother's home, with traces of the dye on a door and car mat.
They were jailed at Birmingham Crown Court.
Det Con Max Gebhard said: "What we have here is a highly-organised duo who were professional in the execution of these robberies.
"They had made extensive plans to try and cover their tracks; both wore masks, they obtained new mobile phones and changed their clothing and footwear.
"Their actions left both delivery men and other staff extremely shaken and distressed."