Plate Numbers for the 80 Cent Documentary

Below is a reprise of two images from my last post.  These two 80 cent documentary stamps with the plate numbers 8438 and 8445 represent half of the plates used to print this stamp.  Due to low demand for the 80 cent stamp only four plates were ever produced, in contrast to dozens for the 2 cent documentary. 

The plate numbers used for Scott number R172 were:

8438

8441

8443

8445

All of these numbers can be found on stamps with both roulettes hyphen holes.  This would indicate all four plates were produced early in the life of this series, sometime before Januarly 1900, and that they were not used so frequently that production of new plates was required to replace worn plates.