How to Identify Your Stamps

The biggest reward from collecting stamps is your enjoyment!  However, at some point you may want to learn the basics of identification and condition of your stamps.  As you may know, two stamps can look exactly the same, and yet they are different issues with different Scott Numbers and values.  Also, you know the difference between used and unused, but do you know how unused and mint stamps differ?  Let me show you some techniques for identifying your stamps!

Used, Unused, and Mint Stamps

First of all – a used stamp has actually been used for postage.  It has a cancellation on it, and usually the gum is missing.  An unused stamp has never been used postally, but may have small imperfections such as a thin or a small tear.  A mint stamp is fault-free. Depending on a stamp’s year of issue, it may be considered mint even if it’s missing gum or was previously hinged.  Stamps pre-1940 can have hinge marks and still be considered mint.  Stamps pre-1890 can have no gum and be considered mint, regardless of whether or not they were issued with gum.

Determining Basic Information

Now, getting back to those stamps which look alike… you need to determine some basic information.  To do this, you must have access to a Mystic Catalog, website or some other publication which describes the various issues of stamps.  As an example, we’ll use U.S. #333 and #426.  Both are 3¢ violet stamps with the same design of George Washington.  If you look at the beginning of their listing, you’ll note the #333 is a perf. 12, with a Double Line Watermark, while the #426 is a perf. 10, with a Single Line Watermark.  The only way to tell these two stamps apart is to measure their perforations and watermark them.

Sheets, Coils, Booklet, and Self-Adhesive Stamps


Some stamp designs look the same, but have been issued for different purposes.  The only difference when you look at them may be the number of sides with perforations.  A sheet stamp has perforations on all four sides.  Coil stamps are issued in long strips for use in vending machines.  They have straight edges on opposite sides and perforations on the other two sides.  Booklet stamps come from a small pane or block of stamps which is part of a booklet sold at post offices or in vending machines.  These stamps can have straight edges on one, two, or three sides.  Self-adhesive stamps are issued on a special backing paper.  Once peeled off the backing, a pre-applied adhesive allows the stamps to be affixed without being moistened.  They may have wavy, “serpentine perforations” or be imperforate.

Self-Adhesive Stamps

Self-adhesive stamps are issued on a special backing paper. Once peeled off the backing, the adhesive allows the stamps to be affixed without being moistened. If you want to put mint self-adhesive stamps in your album, don’t remove the backing paper!

Most US stamps issued today are self-adhesive. They have wavy, “serpentine” perforations or no perforations at all. In fact, self-adhesive stamps don’t always “follow the rules” of water-activated stamps. For example, a self-adhesive booklet stamp may have perforations on all sides or no perforations at all!

Gauging Perforations

Always take the horizontal perforation measurement first, then the vertical.  Make sure the circles on your perforation gauge fit perfectly between the stamp perforations.  After you have determined the perforations, it’s time to watermark.


Sometimes the only difference between stamps that look alike is their watermark.  Watermarks are letters or patterns impressed into the paper used to produce certain stamps.  Modern U.S. stamps don’t have watermarks, but many older ones do, in the shape of a single line or double line U, S, or P.  See illustrations below.

Watermarks were introduced as a way to deter counterfeiting. To see if your stamp has a watermark, place it face down in a watermark tray, and pour enough watermark fluid over it to cover completely.  (Never use water.)  The watermark should be visible; how well it shows varies with the stamp.  You may not see a whole letter or design, but only part of one.  Let your stamp dry completely before removing it from the tray.  U.S. watermarks are always letters like those shown.  (Many foreign stamps have watermarks in the shape of a crown or other symbol alone or in addition to letters.)

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