Vintage 1 quart Blue Ball Mason canning jar, numbers on bottom or symbols?

Description

Waves, bubbles and imperfections tell me this is an older jar.  Symbols on the bottom , seems to be a reverse 2 and 6 also an x and there is the bubble in the middle like older depression glass items.  As with my previous jar sales I know nothing about them.  It seems to be in wonderful condition with maybe a little roughness or flea bites around parts of the rim.