• In the days when a pay telephone call was a dime, some people would put pennies in a dish and add some nitric acid. As the fumes cleared, the coins lost some size and weight. Those that were closer to a dime in size and weight would work in coin telephones, subway turnstiles and other vending machines.
    The practice was not too widespread, since it was not easy to acquire nitric acid — mostly from school chemistry labs — and the fumes were quite toxic. A few of these shrunken pennies show up now and then, and people think they have discovered some rare mint error coins.

• The Secret Service often puts on public displays of counterfeit currency for bankers, business people and even the general public. Some of the more ingenuous examples are genuine $2 bills that have been altered to appear to be $20 bills.
    Since most people would not be aware of the Jefferson portrait on the bills instead of Jackson, that part of the bill escapes close scrutiny. The numerals "2" are changed to "20" and the word "TWO" is also altered to "TWENTY." The remaining elements such as serial numbers, the Treasury seal, and scrollwork remain untouched and original. Again, most people are unaware of the reverse design of either note, so an altered $2 bill could pass rather easily for a $20 bill.
    Fortunately, not too many such fabrications have been discovered. Perhaps they are just too good to be detected? Look in your wallet right now and check.

• Vending machines manage to accumulate all sorts of foreign coins and other round objects that work in lieu of real U.S. coins.
    Because most Canadian coins are magnetic, they no longer work in U.S. vending machines. However, coins from such diverse countries as India and Colombia find their way into subway turnstiles (before NYC went to electronic passes), coin telephones, and food vending machines. The United States quarter is perhaps the most widely copied coin in terms of foreign coins — often worth much less than 25 cents.
    The company that processes Los Angeles' parking meters sends literally tons of foreign coins every year to outside buyers — usually at scrap metal prices. One TV episode of a New York City crime drama showed a street vendor selling Colombian 20-centavo coins to subway riders to use in lieu of quarters (when 75 cents was the fare). Another New York City tale included the Connecticut Turnpike tokens (37.5 cents), which also worked in NYC subway turnstiles at 75 cents. The NYC Transit Authority would send all of these tokens back to New Haven, Conn., to be redeemed for the full fare. Connecticut immediately changed its turnpike token to a smaller-sized version.

• Many years ago, the Pico Rivera (Calif.) Coin Club met monthly in a local bank conference room. The bank canceled the meeting contract when it found its food and candy machines full of quarter-sized Mexican 20-centavo coins the day after a coin club meeting. The coin club disbanded shortly thereafter.

• For its 10th anniversary, the Whittier (Calif.) Coin Club issued a brass token (1959-1969), which happened to be the same diameter as a silver dollar but was quite a bit lighter in weight. In 1970, I was contacted by the security office of a Las Vegas casino, saying they found dozens of these tokens in their $1 slot machines
    After checking out the story, it was discovered that the company that made the tokens had several hundred leftovers that were imperfect in one way or another and sold them for scrap. Whoever bought them for scrap discovered that they work in slot machines. Fortunately, the Whittier club was not held liable for their misuse.

    Dr. Sol Taylor of Sherman Oaks is president of the Society of Lincoln Cent Collectors and author of The Standard Guide to the Lincoln Cent. Click here for ordering information.