The 2D/2C 15c Guemes 'Servicio Oficial'

Up to before looking through this batch of stamps, I had not come across a diffused Straight Rays printing of this stamp. Here it is, the 15cMG2D-SO, a rare stamp.





The overprint has a peculiar letter.



Here are examples of the watermark.





Here is the much more common clear Straight Rays printing, the 15cMG2C-SO, with examples of the watermark.