Black’s sheets were photo-reduced and color-coded by exchange for practical handling.

Evidence

Even the physical size of Black’s sheets was well judged. They had first to be printed on the large computer line-printer paper of the period, but they were then photo-reduced onto standard-size paper, differently colored for options traded on different exchanges. The resultant sheets were small enough for easy handling, but not so small that the numbers became too hard to read. — Donald MacKenzie, An Engine, Not a Camera, 721

Categorization

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