An extraordinary collection of photographs and mementos chronicling the affair of a German businessman and his secretary in the late 1960s and 1970s has gone on show in New York. The memorabilia was discovered in a briefcase three decades after the affair took place, abandoned in a German apartment and later sold at auction. In a dangerous move for an adulterer, businessman Günter K kept a meticulous account of his relationship with a 24-year-old woman known as Margret S who was also married. An extraordinary collection of photographs and mementos chronicling the affair of a German businessman called Günter and his secretary Margret (pictured) in the late 1960s and 1970s has gone on show in New York . The contents of the case, which are on display at the exhibition Margret: Chronicle of an Affair – May 1969 to December 1970, included hundreds of pictures of Margret in various places and poses: sitting at a typewriter at the office, travelling or in hotel rooms, undressing, changing, or getting dressed. Günter kept ticket stubs, contraceptive packets and even locks of his lover's hair. The typed notes and diary entries from the Cologne businessman, who seemed to have an eye for detail way ahead of his time, reveal that he was 39 when the affair began in May 1969. The pair started their affair while on business trips and eventually escalated to them playing husband and wife in Günter’s store building, where Margret prepares light meals and they watch television together. she also gets dressed up in the clothes her love buys for her. The memorabilia was discovered in a briefcase three decades after the affair took place, abandoned in a German apartment and later sold at auction . In a dangerous move for an adulterer businessman Günter K kept a meticulous account of his relationship with a 24-year-old woman known as Margret S. who was also married . Susanne Zander is director of  the Gallery Susanne Zander / Delmes & Zander in Cologne and Berlin, Germany, which own the Margret collection. She said: 'It seems clear that he was obsessed with the process of documenting and collecting. Presumably because he wanted to control both Margret and the situation. 'Somehow he was very 'German', writing down everything in a very correct and precise way – even if what he recorded was deeply personal and often emotional fraught. 'You get a sense of him trying not to lose control of the situation through his obsessive cataloging and archiving. The exhibition Margret: Chronicle of an Affair – May 1969 to December 1970, includes hundreds of pictures of Margret in various poses . Günter kept ticket stubs, contraceptive packets and even locks of his lover's hair . Blogger Messynessychic observed how the pictures reveal the transformation of Margret from, 'a shy, simple, mousy-haired girl to a modern, sophisticated woman with a fiery red high-maintenance beehive do.' The relationship appears to come to an end just before Christmas in 1970 when reports and photographs of Margret begin to break off. According to Günter’s notes, she tells him that 'after Christmas the f***ing will be over and you will not dance at two weddings anymore.' The letters and journals entries provide a porthole into the behaviour of men and women in the 1960s and 70s. The typed notes and diary entries from the Cologne businessman, who seemed to have an eye for detail way ahead of his time, reveal that he was 39 when the affair began in May 1969 . Over the course of the affair Margret seems to transform from a shy girl to a feisty, independent woman complete with a fiery red beehive . Ms Zander said: 'The images tell us about the fashions, styles, and culture of the times but also about the unfolding sexual revolution of the era (1969/1970): even bourgeois Gunter seems to be participating in this social revolution. 'The archive also tells us a lot about the dynamics between men and women at the time: he is older, her boss, wealthy; she is his secretary, younger, pretty, full of cliches. 'Their affair took place at the beginning of the era of women's lib etc. but its clear that the dynamics between Gunter and Margret were far from equal.' The relationship appears to come to an end just before Christmas in 1970 when reports and photographs of Margret begin to break off . According to Günter’s notes, she tells him that 'after Christmas the f***ing will be over and you will not dance at two weddings anymore. The extensive collection of several hundred images is considered to be one of the most detailed collections of memories ever to have been discovered. Ms Zander said : 'The mixture of writings, artifacts, and photographs is, I imagine, extremely rare. 'It is unlikely that another such collection exists. 'Even in our current times of social media – its seems unlikely that anyone has documented a private affair to such an obsessive degree. Which makes this collection of photographs, writings and artifacts from the late 1960s /early 1970s all the more unusual. 'The quality of the photographs is amazing, even if it’s clear that were made by an amateur, albeit evidently gifted, photographer. Both Margret and Gunter are believed to be dead. Ms Zander added: 'Margret is also beautiful and a compelling character. 'Their story is amazing and it is also a document of the time: you get a real sense of the time and place based solely on why Gunter decide to record.' ‘Margret’ is presented in parallel to the exhibition ‘System and Vision’ organized by Delmes & Zander at David Zwirner, New York. February 28 – April 18 . Günter kept ticket stubs, contraceptive packets and even locks of his lover's hair . ‘Marget’ is presented in parallel to the exhibition ‘System and Vision’ organized by Delmes & Zander at David Zwirner, New York .
German businessman and his secretary had an affair from 1969 to 1970 . Pictures and memorabilia found in an abandoned briefcase decades later . Snaps feature the flame-haired object of his affection in a variety of places . Collection now on display in New York art gallery .