There are some pretty convincing articles in the archive by those in the printing business expaining how the stock in wgich the graphics were printed on is that [not true white] color before it reaches its 'all-white' state on the sheets/rolls.

We see very few examples of what you illustrate... especially with the thousands of chips we find out in the field that have been basking in the sun at flea markets and are still in their original inlay stock color.

As I noted, those who have explained the printing process have explained it well... and your example just might be the results of what's been explained in those articles.