The restoration of obliterate serial number can be done in several ways, and the most common method that has been used in this time is chemical etching. However, the problem due to destructive of the metal surface after acid etching can be occurred. Therefore, to find out the effective and non-destructive method is needed. According to alteration of magnetic properties of the specimen’s surface after polished and magnetic-optic nanoparticles. Magnetite (Fe3O4) nanoparticles were synthesized by chemical Co-precipitation method, Then, the precipitation process occurred immediately, promoting a color change in the solution to dark-black, characteristic of the magnetite. Fourier transform infrared Spectroscopy was used to confirm the formation of Fe-O band.But we can found Fe-O group in spectram.