Traditionally if you wrote a letter on someone's behalf (eg they instruct you by phone on what to say and to get it in the mail as fast as possible), you sign is 'PP J. Smith'. PP is short for 'per procurationem' meaning 'by the agency of'. You don't need to know Latin, just that 'PP [name]' means it was sent on someone's behalf.

If I got a letter with no indicator and it turned out to be someone's secretary I wouldn't be offended exactly but it would make me a little wary until I was more familiar with the person and their working habits, eg maybe they have total trust in their secretary, but the secretary isn't familiar with this convention.

Obviously I'm a bit old-fashioned about these things, bt these conventions came into being for good reason.

Today, no. But if I lived in a time when you could expect that a handwritten letter from the CEO was actually handwritten by the CEO, then maybe I would, because in that time, doing that would have been deceptive.

Did that time ever exist? I've gotten the impression that dictating a letter to one's secretary has been a pretty standard thing for at least the last hundred years.

Depends on context, but at a smaller company we did receive them during fund drives and such. Wasn't thrown on a copier or whatnot, but then he only had to do about two dozen. Slight variations but he did follow a script.

So I would put it down to scale and what they feel is important. In that case it was for the local children's hospital. Secretaries are great when you need it written right, not only correct.

More like three or four hundred. And before that, replace "secretary" with "scribe."