All the reasons mentioned above will definitely affect whether or not a penny will read like a dime on the Safari. The #1 reason appears to be rather or not the penny is a pre-84 and then everything else comes into play, especially the moisture content of the ground. When a coin has a questionable dime reading, to try and get a more accurate reading I'll sweep the target several times and sometimes from different directions, often stopping at the end of a swing for a second or two, to see if the Safari will show a different number, especially if nulling (I don't hunt in all-metal). Sometimes by doing so you will get a more accurate TID reading on a later swing. Also pay really close attention to any variations in your numbers, especially when any numbers lower than 38 show up. If you are getting a 36-37-38 reading by sweeping several times, then chances are very good that it is a penny. but be careful as I just had a 37-38-39 reading be a deep silver. The last time out I made a conscious effort to avoid digging any pennies and still close to 10% of my coins ended up being pennies that were reading and sounding like dimes, so no method is infallible. One other thing, usually (not always) on the Safari a penny will have a slightly different tone than your dimes or quarters. Over time you will begin to get better at noticing the subtle differences between them. You can also use the difference in tones as a reason to dig those targets reading a 37 or like a high penny, but actually sounding lke a dime. Sometimes they will turn out to be a deep dime rather than the normal penny. Just for the record on my Safari a penny will "normally" read 35-37, sometimes lower. A dime and quarter will usually read 38 with a quarter sometimes reading as high as 39. If you want a detector that I.D.'s pennies really well, try the XT-70 (705), but it usually won't give you quite the depth of a Safari.
