A casing in which a set of metal parts is formed from the same metal of at least a predetermined purity and the elements are individually severable from the casing without retaining residues that will effect the purity of the items. The memory module may also include a switch connected in parallel with the data buffer, wherein the switch can selectively bypass the data buffer. even when the internal combustion engine is switched off and the stored number of teeth is used to determine the initial angle position of the internal combustion engine. Steel layer could be made of coiled steel wire springs.