I did notice the shifted text appeared more orange than yellow. Since my grandad doesn't seem to have a duplicate of this particular stamp I did a quick Google search for an image of it just to compare.
Found a site called bardostamps.com which had a bit of information (and a nice image) of the stamp.
Quantity Printed: 161,235,000 (Pane: 50) #8212; Bureau of Engraving and Printing (BEP)Does the "Pane:50" mean that it was sold in a sheet of 50 stamps? (sorry if this is a dumb question)
Thanks!