From a 1907 Gregg Speed studies book, but it's not a business letter, so you might find it interesting to copy in shorthand. it does have timing marks, 25 standard words, so you could even do a dictation if you want.
"Gregg Shorthand had achieved the most extraordinary success ever attained by any system in the history of shorthand." John Robert Gregg, 1922
This letter has some "teaching" ideas under it for the students. They were to think about the letters or articles they were taking dictation from. So the numbers to the footnotes are those. These were counted in 20 words by a bold veridical line.