Assembly comprising: - a pince-nez moulded in one piece and comprising a substantially planar structure which has a first rim provided with a first lens and a second rim provided with a second lens, said structure having a plane (n) which passes through said first and second rims (2A, 2B) and said first and second lenses (3A, 3B), said first and second rims (2A, 2B) each being extended by a linkage which connects them together, said linkage being arranged to be in contact with a holding element intended to be placed on the nose of a user, said linkage being curved and having a first and a second point of inflexion (8, 9), said pince-nez having a first ready-to-wear position wherein the pince-nez is arranged to be placed on the nose of a user and wherein the linkage is in the idle position where the first and second points of inflexion (8, 9) are distant from each other and a second position wherein the linkage is in a tension position wherein the first and second points of inflexion (8, 9) are close to each other; - a holding element intended to be secured to the pince-nez, having a curved shape and comprising a first and a second point of inflexion (6F, 6G); - a case intended to contain the pince-nez, provided with the holding element, said case having a first rim and a second rim and a linkage element connecting said first and second rims to each other, said first and second rims being spaced apart from each other by a distance d corresponding to the length of the case and being arranged to hold said pince-nez in the second position, when said pince-nez is housed in said case, said assembly being characterised in that, when the pince-nez is housed in the case, the entire structure thereof is housed in the case except for the linkage and the holding element, which remain visible. - a pince-nez moulded in one piece and comprising a substantially planar structure which has a first rim provided with a first lens and a second rim provided with a second lens, said structure having a plane (n) which passes through said first and second rims (2A, 2B) and said first and second lenses (3A, 3B), said first and second rims (2A, 2B) each being extended by a linkage which connects them together, said linkage being arranged to be in contact with a holding element intended to be placed on the nose of a user, said linkage being curved and having a first and a second point of inflexion (8, 9), said pince-nez having a first ready-to-wear position wherein the pince-nez is arranged to be placed on the nose of a user and wherein the linkage is in the idle position where the first and second points of inflexion (8, 9) are distant from each other and a second position wherein the linkage is in a tension position wherein the first and second points of inflexion (8, 9) are close to each other; - a holding element intended to be secured to the pince-nez, having a curved shape and comprising a first and a second point of inflexion (6F, 6G); - a case intended to contain the pince-nez, provided with the holding element, said case having a first rim and a second rim and a linkage element connecting said first and second rims to each other, said first and second rims being spaced apart from each other by a distance d corresponding to the length of the case and being arranged to hold said pince-nez in the second position, when said pince-nez is housed in said case,