Design error?

(Originally posted at http://joelnoche.multiply.com/journal/item/112/Design-error on September 13, 2012 3:18 AM)

I collected stamps when I was a child and as a result I have a lot of mint Philippine stamps from the late 1980s.  These include blocks, imperforates, and souvenir sheets.

Of special interest is the pair of stamps shown above.  It seems that they have Scott number 1919 and were issued on February 25, 1988.  But the one at the bottom seems to be a design error as it has the incorrect date 1938.

Note that the stamp at the bottom has slightly different colors, messier perforations, and blurrier printing.  If you have any information about this stamp, please leave a comment.  Thanks.