The Seattle Mariners today announced they would be wearing the uniforms of the Seattle Steelheads for their game May 16th against the Boston Red Sox. The Steelheads were a Negro League team based out of the Pacific Northwest in 1946.
Love those socks.
Based on the design we see above, it looks like the Red Sox will be wearing the uniforms of the Boston Royal Giants:
Seattle had previously worn Steelheads uniforms before, 20 years ago in 1995 against the Kansas City Royals (a game so long ago now that it itself could be thrown back to):