A method for verifying a security element comprising a security element body having a window portion, in which the material of the security element body is transparent between a top surface and a bottom surface, wherein the window portion is surrounded and delimited peripherally by a non-transparent region of the security element body, wherein the window portion merges into a transparent window extension which extends into the non-transparent region, wherein, however, the window extension is covered completely non-transparently towards the top surface and towards the bottom surface of the security element body, or a security element produced according to a method of manufacturing a security element, wherein the security element produced by the manufacturing method comprises a security element body having a window portion extending from a top surface to a bottom surface, which window portion is formed of transparent material which merges into a window extension, the transparent material of which is covered completely non-transparently towards the top surface and the bottom surface, wherein the manufacturing method comprises the following steps: providing a core layer which is non-transparent at least in one areal portion, making a recess in the core layer inside the non-transparent areal portion so that the recess is surrounded peripherally by a non-transparent part of the areal portion, inserting transparent material into the recess; non-transparently covering an extension section of the recess towards the top surface and towards the bottom surface and introducing heat to form the security element body, wherein in the verification method, verification light is radiated into the window portion of the security element, at least one image of the top surface or the bottom surface is captured which comprises at least one area adjacent to the window portion, and the image is analysed for differences in brightness in the area adjacent to the window portion, wherein the security element is classified as authentic if in the area adjacent to the window portion an area of increased brightness is detected which is adjacent to the window portion and the verification decision is issued based on the classification, wherein in the verification method a reference image of the top surface is captured accordingly, if at the at least one image is captured from the top surface, or of the bottom surface, if the at least one image is captured from the bottom surface, wherein no verification light is radiated into the window portion during the capture of the reference image, and during the evaluation of the at least one image firstly a difference is formed with the reference image and differences in brightness are determined in the difference image, wherein the security element is only classified as genuine if an area of increased brightness, which is adjacent to the window area, is detected in the difference image. providing a core layer which is non-transparent at least in one areal portion, making a recess in the core layer inside the non-transparent areal portion so that the recess is surrounded peripherally by a non-transparent part of the areal portion, inserting transparent material into the recess; non-transparently covering an extension section of the recess towards the top surface and towards the bottom surface and introducing heat to form the security element body, wherein in the verification method, verification light is radiated into the window portion of the security element, at least one image of the top surface or the bottom surface is captured which comprises at least one area adjacent to the window portion, and the image is analysed for differences in brightness in the area adjacent to the window portion, wherein the security element is classified as authentic if in the area adjacent to the window portion an area of increased brightness is detected which is adjacent to the window portion and the verification decision is issued based on the classification, wherein in the verification method a reference image of the top surface is captured accordingly, if at the at least one image is captured from the top surface, or of the bottom surface, if the at least one image is captured from the bottom surface, wherein no verification light is radiated into the window portion during the capture of the reference image, and during the evaluation of the at least one image firstly a difference is formed with the reference image and differences in brightness are determined in the difference image, wherein the security element is only classified as genuine if an area of increased brightness, which is adjacent to the window area, is detected in the difference image.