I can make out "4500", "MAIN", and what might be "ERIE-9" on the far left edge of the ruler.
These are phone numbers, circa 1910, and still in fairly common usage up until about 1960 in many areas.
The Cleveland City Directory from 1915 lists
all of these phone numbers as belonging to "The Plain Dealer", which was a newspaper founded in 1842, and apparently still around, at least via the web.
Frankly, it is a bit hard to follow all the mergers along the way. It appears the original "Plain Dealer" newspaper acquired two other papers in 1885. These were the Cleveland Herald, and the Cleveland Leader. Concurrent with these acquisitions, the Plain Dealer starts a morning edition. Sometime between 1885 and 1908, the Plain Dealer also starts a Sunday-only paper of the same name. Follow me so far?
In 1905, the
evening edition of the Plain Dealer merges with World-News and that's the last we will see of it here. The rest of Plain Dealer (i.e., morning edition) then acquires the daily portion of the Cleveland Leader in 1917, while the Sunday-only portion is acquired by the Cleveland News. In 1932, The Plain Dealer and the Cleveland News merge to become the Forest City Publishing Company, but both papers continue to operate separately. Forest City Publishing later sells The Cleveland News to the Cleveland Press in 1960.
So, long story short:
Once your ruler is cleaned-up, you will likely see the name Cleveland News, Herald, Leader or Press. (Take your pick?)
As a side note:
The "Leader Building" (as it is now called following that convoluted family tree), still stands at the corner of E 6th Street and Superior Avenue in downtown Cleveland.