Interesting. A lot about the type on your paler triangle looks different. The letters are thicker and many of the rounded letters - D you S - look squared off.
I don't see anything written in my Unitrade about variations. I wonder if you have a forgery? And considering you already have a single and a pair, that might make for an interesting set.
...and a quick google search (my friend google!) turns this up.
Check out the stamp on the upper right on this page. Look familiar?
http://www.geocities.com/claghorn1p.../Newf03a.htm