Page rulers on a Macintosh monitor is determined by the number of pixels available, not by the physical screen size. The Macintosh Classic (and other compact Macintosh 9-inch screens) and the 12-inch RGB monitor are 512 pixels wide, so they display the same ruler length.
Even though the ruler width of the two monitors is the same, the 9-inch monitor is 342 pixels tall, while the 12-inch RGB monitor is 384 pixels tall. The 13-inch RGB monitor and the 12-inch monochrome monitor are 640 pixels wide and 480 pixels tall.
This article was published in the "Information Alley":
Volume II, Issue 12, Page 19
Article Change History:
11 Oct 1995 - Revised entire article to better describe situation.
05 Oct 1995 - Added Info Alley information; updated article.
20 Mar 1995 - Minor typographical error.
Support Information Services