Collection Studio 4.72
[ release date: March 31, 2016 ]
"Test stamps" are not actually postage stamps, not being valid or intended for prepayment of postage, but are for testing printing processes, equipment, and the like.
In the United Kingdom test stamps for coil despensing machines have been known as poached eggs, due to their design. Originally these were printed in green but later black ink was employed with the addition of text denoting their intended use. These british labels were printed in the same format and size as the then current definitives and perforated in the same manner. In addition the amount of ink used on the paper was the same as was used to produce the actual postage stamps, thus they could test the machines with, (as near as possible), the stamps that would be used in general use.