That seems like an awful lot of work just to catch someone stealing a free subway ride…


To trap persons who insert worthless metal slugs in turnstiles, slot machines, and coin telephones, an ultra-violet-ray fingerprinting process has been developed.

Since the conventional “powder” method of bringing out latent prints is unsatisfactory for photographing specimens found on metal surfaces, the print is “fixed” with a chemical reagent, and the slug is then soaked in a dye that becomes luminous under ultra-violet light. Placed in a special viewing apparatus, the slug background glows under the invisible light, while the fingerprint stands out in black lines that can be photographed to make a permanent record for checking against prints of suspected persons.

  1. Hirudinea says: November 2, 201211:06 am

    Cost of slug – 5 Cents, Cost of Fingerprinting – $50, Value of Idea? Worthless!

  2. D says: November 2, 20124:28 pm

    Probably the benefit would be that you’d discourage others from doing it, because they know they could get caught.

    Plus, i’m not sure it really *was* alot of work back then; they probably had “a guy” for it, who just toiled away at that all day as his job. So it’d only be like, one extra employee + some equipment (or maybe he even shared equipment).

  3. dev says: November 2, 20129:11 pm

    What did you do today? Oh I had a bunch of crooks arrested for using slugs for free rides. So wonderful. America is safe at last.

  4. Mike Brown says: November 5, 20127:42 am

    Even in 1937 there were some rules of evidence – a slug is just a round piece of metal, and it’s not against the law to touch a round piece of metal. It’s using the slug as coinage or to obtain services which is illegal (I’m not sure if subway tokens are or were covered by counterfeiting laws).

    Unless they could catch the person actually putting the slug in the turnstile, the fact that their fingerprints were found on a slug collected from a turnstile wouldn’t have proven that they stole a ride, just that at some time they had touched the slug (or the sheet of metal from which the slug was made).

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