I got this lens very cheaply (70 euro) as there was fungus in 3 lens surfaces. I removed the fungus and believe that I put everything back correctly. The lens is indeed a double gaus one. I am not sure but I am pretty confined that there are three doublets inside the lens (a doublet is a lens made from two lenses of different materials in a such way that they cancel each others color dispersion). Pretty expensive construction but results are very good. All photos handheld aperture, 11 and light from Godox ring flash ml-150. 1:2 magnification, resized 25% 100% crop from above 1:1 magnification, resized 25% 100% crop from above Lens is much softer at 2.8 but I think that this lens is too revealing to be used in unprocessed portraits. I think that I am not going to seek another macro lens for a while.