I apologize for the complete lack of enthusiasm, but...... There are likely a THOUSAND similar print variations from the 1950s-1970s Topps issues already discovered and there are likely a 1000 more still waiting to be discovered.
This variation is nothing more than a non-intentional print variation like so many, many others previously "discovered" and posted in the variations thread.
The most likely reason it took until now to notice is that many collectors/dealers don't necessarily have multiple copies of key HOFers such as this to compare to one another, so it takes longer to discover such things on higher profile cards.
This card does not appear to be "rare" by any stretch, just check the completed listings on ebay. There are not only other more well known print variations that are much more rare, there are also other true variations that are far tougher to locate.
FWIW, the article fails to mention some other previously mentioned PRINT variations from the 55 Topps set......see below for a link to Richard D's variation site:
https://sites.google.com/site/richar...riations-lists