Get breaking news alerts and special reports. The news and stories that matter, delivered weekday mornings.

LONDON — Dutch inmates will have the chance to help solve mystery murder cases as police distribute calendars featuring unsolved cases to prisons across the Netherlands.

The so-called cold-case calendars will feature a photograph of a murder victim or missing person, as well as details about the case, for each week of the year.

The Dutch police announced the project last week after a pilot program that rolled out in five prisons in January coincided with a large number of tip-offs.

A page from the cold-case calendar that is being distributed to prisons across the Netherlands this week. Dutch Police

“We got 160 tip-offs in the first five months of this year and we normally get 160 a year,” Robbert Salome, a spokesman for the Dutch National Police told NBC News. Jeroen Hammer, who helped develop the calendar, told Dutch broadcaster NOS that the tip-offs had allowed police to reopen two cases out of the 52 featured on the calendar.

Salome said that while it was impossible to know how many of the tips had came from prisoners — because the informants have the right to anonymity — research has shown prisoners knew a lot about other crimes.

Let our news meet your inbox. The news and stories that matters, delivered weekday mornings. This site is protected by recaptcha

“We know that people in prison talk about crimes,” he said, adding that a study had shown that in 40 percent of court cases in the Netherlands, the perpetrators had told someone about the crime they had committed.

According to data collated during the pilot project, two-thirds of inmates said they thought the calendar was a good idea, according to Salome.

“The murders are all of innocent people," he said, adding that, "these prisoners are proud and have their own codes — you don’t kill innocent women and children. There’s no respect for that in prison.”

Related: Dutch King Willem-Alexander Reveals He Was KLM Pilot

Police are setting aside a total of 800,000 euros ($920,680) from which they can reward individuals whose information leads to a conviction.

The calendars were inspired by a program in the United States, where some states have been giving inmates decks of playing cards that feature the most troubling unsolved murder and missing person cases.

“We didn’t want to play a game with dead people so we came up with the idea of the calendar,” Salome said.

A prison facility in Tilburg, Netherlands, in 2010. Michael Kooren / Reuters

The Netherlands has some 1,500 unsolved crimes classified as cold cases — which are mainly homicides, according to police.

Officers said the 52 cases featured on the calendar were chosen because the public found them particularly shocking.

"Most of the victims on the calendar were people who were in the wrong place at the wrong time and were completely innocent," said Salome. "People are more disturbed by crimes like these than — for example — crime-related killings."

The detectives working on the 52 cases had also said there could be promising developments, according to the Dutch police's website.

Officials have printed 30,000 copies in Dutch, English, Arabic, Spanish and Russian to help reach as many people as possible.