An example of this medallion in a weight was researched by a member of the PCC and PCA, and the findings were first published in the 2002 issue of The Annual Bulletin of the Paperweight Collectors Asociation, Inc.
It was the logo / insignia of a Scottish paper making company called Tullis Russell. The research article states that a former employee of the company remembered these weights being produced in 1959 as a 150th anniversary issue.
As it was dated to 1959, it's one of the few pieces of evidence that can be used to date a Vasart weight.
I have an example but I had to remove the acrylic covering as it had "crizzled" so much that the medallion could hardly be seen. It took several sessions over a couple of days soaking in acetone to get rid of the acrylic!
It's quite possibe that the "blurring" over the medallion as seen in the eBay photo may be the acrylic going off, or if it has already been removed, it could be damage to the medallion itself. It would useful to know which it is.