Character 173 in the Dingbats font, which is a 2 inside of a circle, is missing.
The ZapfDingbats font is not bundled with LibreOffice. The proper Unicode for the character mentioned is U+2777 or U+2781. Both glyphs are present in the majority of the LibreOffice bundled unicode fonts. Some of the font families may refer to the U+2700 block as Dingbats, and may have that listed as a subset but that is not common or required. Simple to work around, if the glyph is not present in one font family shift to another. Trivial to to review glyphs for a font using the Insert Special character dialog.
(OP) > Character 173 in the Dingbats font (Comment #1) > The ZapfDingbats font is not bundled with LibreOffice. Stuart, how you know OP was referring specifically to the Zapf Dingbats font? ;-)
Herman Zaph's Dignbats font done for ITC is the progenitor for the circle/negative circle numbers found in the Unicode U-2700 block. Assumed without checking a ref--the 100 series contains those glyphs, it does although 152, or 162 (rather than 173) are circle number 2. No other source I can find for 173. Either way, invalid as LO deals with Unicode and multiple fonts provide the glyph.
FYI: I guess my problem is with Linux Mint 17.1. Insert > Special Character > Dingbats U + 173 is missing.
(In reply to rebelxt from comment #4) > FYI: I guess my problem is with Linux Mint 17.1. > > Insert > Special Character > Dingbats > > U + 173 is missing. Again LibreOffice does *not* deploy Dingbats as a named font. Although some font families will list it as a subset. So, in what font? U+00AD (173) is a "soft-hyphen", U + 173 would never describe a circled number. In Unitype, in addition to the "Dingbat" U-2700 block, there is the enclosed alpha-numeric block U-2460-24FF. Look for the glyph there in one of fonts present on your system (LibreOffice deployed or otherwise for your DE).
I accept that my missing character is not a LO problem. However, on my system, which is Linux Mint 17.1, when I start LO calc, click on the Insert menu, select Special Character, then the font Linux Mint has named Dingbats, the circle 2 character is missing. The Insert Special Character dialog says this character is U+173. Obviously this is not the actual Unicode designation, but that's what it says. I have no idea where a little nit like this could be picked, and was kind of hoping somebody could pass it upstream to whoever. Thanks for reading my rant.