What else stands out in the picture?

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Obviously, any number of things can provide a satisfactory answer to such a broad question, depending on your perspective. The answer we're looking for is ... this screen shot provides the earliest known appearance of a cleat cleaner affixed to the back of a Major League mound! If you asked me when cleat cleaners became a ubiquitous part of the MLB experience, I'd've guessed somewhere around 2000, with the Mets adopting it for their home park neither earlier nor later than the mean MLB team, but apparently, the Mets have had cleat cleaners on their mound longer than they've had blue walls!
All this and more, in a deep-diving piece on cleat cleaners from Fangraphs!