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This is a crosspost from the Mathematics Stack Exchange (original post there deleted), I thought I'd ask here as well in case anyone knows. In the STIX package there is a character called \rangledownzigzagarrow, which corresponds to U+237C ⍼ RIGHT ANGLE WITH DOWNWARDS ZIGZAG ARROW in the Miscellaneous Technical Unicode block. What is it meant to represent? Are there examples of its usage?

According to the STIX project, the character is copied from ISO/IEC TR 9573-13:1991, which in turn obtained the glyph from the Association for Font Information Interchange's registry for glyphs in accordance with ISO/IEC 10036. (I've written up the trail here for the curious.) Going by this email from Asmus Freytag, it sounds like anyone could have registered a glyph with AFII for a fee, so the trail kind of goes cold there.

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This symbol was "adopted" from the existing ISO 9573 standard which defined entities for use with SGML. It appeared in the entity set ISOAMSA, which, regardless of the name, had no connection with the American Mathematical Society; instead, it means "added math symbols", as evident in this listing. I had no idea what the symbol meant or was used for, thus assigned it a "descriptive name" when collating the symbols for the STIX project. (I still have no idea, nor can supply an example of the symbol in use.)

A rather unwieldy position-specific table containing information on the collection submitted for consideration by Unicode can be found via links on the web page https://www.ams.org/STIX ; this is not the final table, which was updated after Unicode assignments were made, but I was pulled from the project before I could complete the tidying up. I am now retired from AMS, and no longer have access to the paper records used to compile the collection; those were left with the intention that they be properly archived, but I have no knowledge of what may have happened to them since.

Paying more attention to the information provided in the question, it is the case that ISO 9573-13 existed long before either AFII or the STIX project were formed. 9573 was an adjunct to the SGML standard, compiled by the same or associated people. I once asked Charles Goldfarb what the source of these entities was, but remember that he didn't have a definitive answer.

Addendum
Even though this question is now closed, there's more useful information available. The OP has done some heroic archaeology, and found among archives holding Monotype punches the actual punch used for producing type for this symbol. A photo of the punch is included in this blog entry. It may have been a special order. The shape differs from the one currently shown in the Unicode charts (I'm going to try to get that fixed), but it's indubitably the same symbol. And we know by this that it appeared in print at one time. But the meaning is still not known.

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    Ah, so it was added to AFII because it was in 9573-13, and not that 9573-13 simply included all of the AFII entries? I didn't find the character in ISO 8879 on SGML, so it seems like it was added to SGML some time in between the two...
    – ionchy
    Apr 13, 2022 at 1:32
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    Many sources think that "AMS" stands for "added math symbols". This character is from "isoamsa" arrow relations. There is also "isoamso" ordinary, "isoamsc" delimiters, and "isoamsr" relations among many others: mit.edu/afs.new/sipb/project/sgml/share/sgml/catalog
    – A. Rex
    Apr 13, 2022 at 14:17
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    Wow. A post from Barbara Beeton with actual, real, capital letters. Do I remember correctly that this means that this is an official stance of the AMS?
    – mbork
    Apr 13, 2022 at 16:03
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    @mbork -- The all-lowercase mode was significant while I was still employed, to differentiate between "personal" and "official" communications. I retired from the AMS in February 2019, so the distinction no longer matters; all responses are now all my own. Apr 13, 2022 at 16:23
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    This answer to the original question on Maths SE sheds some more light, saying it represents a Y-axis continuing below the X-axis, and was used in Dutch economy textbooks.
    – PJTraill
    Apr 13, 2022 at 19:28
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There was just a YT video about it: https://youtu.be/cCoed5Oo_J4

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    (this is a bit link-only I guess...)
    – user202729
    May 6, 2022 at 23:48
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    The information in the video is inaccurate. It fails to recognize that the inclusion of the character in the STIX collection was based on its presence in a version of ISO 9573-13 earlier than the 1991 version cited, a version which existed long before AFII was formed. So any claim that it originated with AFII is chronologically invalid. May 7, 2022 at 18:21

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