Wonder Color Gauge

When you get it be sure to send it to me so I can check for authenticity. I will be sure to get it back to you (now where did I put your address??)

I have a Wonder color gauge. Although i'm not very into classic stamps I use it once in a while. For example the carmine pink look similar to the dull pink on the gauge so if you have only the colors to distinguish two stamps it's very hard for a non-specialist. Since it's not accurate I always check the perfs and the watermarks even the paper. Color gauge come last when everything else is equal. Building a guide with real stamps I heard that before. Would be fun to do. Nice contribution khj

I use a very old Wonder Color Gauge, at least I think it is old.
All of the cards say Copyrighted 1940, but no actual date.
Since it was from my Grandma's collection, I am assuming about 1940.
Is there any way to tell the age from the Plastic envelope?
Also, even though they are kept in a dark cabinet, is there any way
of knowing if the color shades are still accurate?