This is the documentation of Computed Tomography (CT) data of a pen-spring. It can be freely used for scientific purposes with appropriate references to the data and to this document in https://arxiv.org/abs/1907.01871. The provided data set includes the X-ray sinograms finalSino of a single 2D slice from a different height of the spring. The finalSino was obtained from a measured 10-projection or 100-projection sinogram using fan-beam geometry by down-sampling and taking logarithms. The data set includes also those original measured sinograms and corresponding measurement matrices.