Reference to a letter of Sept. 10, 1888 signed Jack the Ripper

[Chris Scott]

In the same long article which I mentioned in the "Mary Kelly and the merchantman captain" thread there is a reference which I found intriguing.
The article makes reference to a letter, signed Jack the Ripper, dated 10 September 1888. From the description I am pretty sure this is not just a garbled reference to the Dear Boss letter, as the writer says the letter was posted in Belfast (Northern Ireland) and contained a threat to kill ten more victims and was sent to a newspaper.
Any ideas or thoughts?

Article from the New York Sun, 25 Nov 1888

[Chris Scott]

The transcription:
This "Jack the Ripper," who is committing these murders, is so called because after one of the more recent murders a newspaper in London received a letter from Belfast, dated Sept. 10, in which a man signed himself in that way and said he meant to kill ten more women. His first crime occurred nearly a year ago, in April. But little attention was paid to it and no description of it has ever been published here. A woman was found murdered in the streets and her mutilation was so peculiar that when the other crimes were added to this the similarity of the man's method of treating his victims called the first one to mind. This first victim was Emma Elizabeth Smith.

[JTRSickert]

I think it is just a misprint. It sounds like they are combining two elements of 2 different stories and that they got the facts mixed up. I think the communication on Sept. 10th about killing ten more victims is a reference to the myth that there was graffiti at the site of Chapman's murder. The graffiti allegedly said, on the fence, "Ten more and I give myself up." And then, they take the signature of "Jack The Ripper" that was first heard from the Dear Boss letter. Remember, this article came out in late Nov., 1888. By this time, everyone was referring to the Whitechapel Murderer as JTR, rather than Leather Apron or Whitechapel Fiend, etc. So, My best guess is that the newspaper took those 2 facts and mistakenly combined them into one story, making it seem as though the "ten victims" reference and "Jack the Ripper" signature appeared on a Sept. 10th communication.