Lee, W. J.

Wolfer, D. A.

English

Northwestern University Illinois, School of Law: Scholarly Commons

Journal of Criminal Law and CriminologyVolume 50Issue 5 January-February Article 16Winter 1960Application of Magnetic Principles to theRestoration of Serial NumbersD. A. WolferW. J. LeeFollow this and additional works at: https://scholarlycommons.law.northwestern.edu/jclcPart of the Criminal Law Commons, Criminology Commons, and the Criminology and CriminalJustice CommonsThis Criminology is brought to you for free and open access by Northwestern University School of Law Scholarly Commons. It has been accepted forinclusion in Journal of Criminal Law and Criminology by an authorized editor of Northwestern University School of Law Scholarly Commons.Recommended CitationD. A. Wolfer, W. J. Lee, Application of Magnetic Principles to the Restoration of Serial Numbers, 50 J. Crim. L. & Criminology 519(1959-1960)APPLICATION OF MAGNETIC PRINCIPLES TO THE RESTORATIONOF SERIAL NUMBERSD. A. WOLFER AND W. J. LEEThe authors comprise the staff of the Firearms and Explosive Unit, Criminalistic Section, ScientificInvestigation Division of the Los Angeles Police Department. This article is based upon a report givenby them at the 13th Semi-annual Seminar of the California Association of Criminalistics sponsoredby Los Angeles State College. Mr. Wolfer has been a member of the Los Angeles Department since1950 of and the Scientific Investigation Staff since 1951 and is a part time instructor and lectureron scientific investigation subjects at Long Beach State College. Mr. Lee likewise joined the De-partment in 1950 and the Scientific Investigation Staff as a safe and lock expert in 1951. His assign-ment with the Firearms Unit came about three years ago, and he likewise serves as a part time in-structor in scientific investigation in subjects at El Camino College, Los Angeles.-EIoO.The purpose of this article is to provide personsinterested with a simple and inexpensive methodbased on basic magnetic principles for restoringobliterated serial numbers and identificationmarks. This technique is applicable to guns,business machines, hub caps, small motors, andother metal objects. Although in many cases itproduces the desired results where acid etchingfails, the reverse is also true wherein acid etchingwill be found to be more desirable. A specific casewhere this is known to be true is in the case ofcarbines and submachine guns where acid etchingusually fails, but this technique is successful.MATERIALS1. One horse shoe magnet (approx. 125 lbs. pull).Cost ranges from $8.00 to $18.002. One small vibrator (hand type). $4.00 to$25.003. Fea0 4 (OUS) Magnatite-screened through300 or finer mesh and suspended in a carriersuch as Base Oil "C". Usual cost 8.50 pergallon or one (1) Magnaflux prepared bath"9 BM". $2.25 per pintPROCEDUREThe surface to be restored is prepared in thesame manner as is necessary for acid etching (re-JIsgure IA metal piece from a sewing machine, in which there is suspicion that a serial number was removed and anew number stamped is shown in position at the tips of the magnet.519D. A. WOLFER AND W. J. LEEFigure 2The restored serial number reading 5158 is shown developed by this magnetic process. A partial outline of thefirst five can be detected in the area under the second 8 of the new serial number 81187.moval of gross markings and polish surface). Finerdetails in this method appear better on highlypolished surfaces. It is recommended that crocuscloth and steel wool be used as a final polishingmedium.The object is then placed directly on the magnetso that the concerned area is centered between thetwo poles (see figure 1). The vibrator is then helddirectly on the magnet or the object and the solu-tion applied in moderation to the concerned area.Restoration occurs almost instantaneously; how-ever, longer vibration may be required. A con-venient dispenser for the magnatite bath is an 8 oz.polyethylene wash bottle with a polyethylenespout.After the formation of the numbers, photographscan be taken immediately or the object may beallowed to set until the carrier has evaporated andthen photographed. (See figure 2). This techniqueeliminates the destruction normally accompanyingthe use of acids or heating.(Vol. 50

Application of Magnetic Principles to the Restoration of Serial Numbers

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Application of Magnetic Principles to the Restoration of Serial Numbers

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