As reported by IGN, the minutes are raster files corresponding to the digitization of the handwritten paper maps preserved in the IGN Technical Archive. This is the work leading up to the completion of the National Topographic Map, in some cases several decades apart from the publication of the first edition of the MTN of the area. This type of documents were mainly made between 1870 and 1950 and are classified into planimetric minutes, altimeymetric minutes and joint minutes of altimetry and planimetry. Drawn at 1:25,000 scale, with an accuracy of obtaining the corresponding information at 1:50,000 scale.
From the minutes was made the first edition of the National Topographic Map (MTN) scale 1:50,000, where we can observe the improvement and homogenization of the cartography. The work was completed in 1968 and has 1106 maps covering the entire territory.
From both jobs we can download the georeferenced raster files from the IGN download center: http://centrodedescargas.cnig.es/CentroDescargas/index.jsp