Hello everyone.....
I bet I'm the only one here that collects perf gauges.
My oldest is the top center one from the 1930's....France. I think I have about 9 different types now. There's one here I've used so long I've actually worn off the markings, probably used it about 20 years and another almost as worn.

The old metal type can only measure whole & half sizes such as 10, 10 1/2, 11, 11 1/2, 12, 12 1/2 and so on.....
The new clear plastic type can measure those plus the serpentine type that have sizes such as 10, 10.2, 10.4, 10.6, 10.9, 11, 11.4, and many more sizes....on or off cover.....consider the Flag over Porch series....25+ varieties with serpentine perfs that can only be properly identified by the perf measurements. Most have minimum value but there are several worth $50.00+ and a few worth hundreds of dollars.
As you can see these perforations line up with the dots extremely closely. A perf 8 will not line up with any other, nor will a perf 12, or 15.
Two of these have a value of 35 & 40 cents.....the other has a value of $4.00....if they were yours wouldn't you want to know which is which ?

There are 64 varieties of this two cent red ranging in value from pennies to thousands of dollars.........collectors absolutely need perf gauges and we also need to be able to check for watermarks..

These are the 2 main types of WMs for older US stamps, they stopped using them in the 1940's or early 50's.

Here's how they look in WM fluid. Sometimes there is only a very tiny mark when the stamps are printed and perfed out of alignment so it's very important to practice checking watermarks. (The double line WM stamp is shown upside down)
