Which came first: the blue, or the diamond?

Hindsight bias is a powerful thing.
For pen people, the Blue Diamond guarantee mark is indelibly associated with Parker. So when I recently catalogued some pens and pencils made by Parker for resale by Sears under their Diamond Medal and Webster house brands, I didn't think twice before writing that their imprints incorporated the Parker diamond logo. And then, the realization suddenly hit me: these Sears imprints were from the mid-1930s, a few years before Parker first put the Blue Diamond on its own pens. Whose logo was that diamond anyway?

I have not had much luck with my trademark search efforts so far, but the diamond in these imprints was already part of Sears' Diamond Medal logo back in the 1920s.

Originally posted by ToasterPastry at Fountain Pen Network

Without the medal, however, the diamond by itself would not have been an easy trademark to defend. Diamond Point had been using a diamond-shaped logo (with lettering inside) going back to the hard rubber eyedropper era. So when Parker began using the Blue Diamond as its lifetime guarantee mark in 1939, Sears might not have been able to do much about it -- the question remaining open, however, regarding Sears' opinion of the "borrowing".

In a recent article Jon Veley makes a compelling case that Sheaffer's White Dot was copied from Dunhill's White Spot -- an instance of trademark appropriation that was entirely legal, since Dunhill's mark had been registered for "tobacco products" and not for writing instruments. The background to Parker's Blue Diamond mark differs, in that both the Blue Diamond and its precursors were registered for the same class of items, color being added to set the marks sufficiently apart. Nonetheless, it now appears that both of these two famous pen trademarks were not purely original creations.