Cannot convert string to type Fontstruct

The string in question is "-*-helvetica-bold-o-normal-*-12-*-*-*-*-*-iso8859-1". I have xorg-x11-fonts-ISO8859-1-100dpi-7.5-9.el7.noarch.rpm installed, so I should have this font, and indeed I believe I do.

% ls -l /usr/share/X11/fonts/100dpi | grep helvBO12
-rw-r--r--. 1 root root 5445 May 5 2014 helvBO12-ISO8859-1.pcf.gz
-rw-r--r--. 1 root root 15768 May 5 2014 helvBO12.pcf.gz

Yet,

% xlsfonts | grep -i helvetica-bold-o-normal
-adobe-helvetica-bold-o-normal--11-80-100-100-p-60-iso10646-1
-adobe-helvetica-bold-o-normal--11-80-100-100-p-60-iso8859-1
-adobe-helvetica-bold-o-normal--14-100-100-100-p-82-iso10646-1
-adobe-helvetica-bold-o-normal--14-100-100-100-p-82-iso8859-1
-adobe-helvetica-bold-o-normal--17-120-100-100-p-92-iso10646-1
-adobe-helvetica-bold-o-normal--17-120-100-100-p-92-iso8859-1
-adobe-helvetica-bold-o-normal--20-140-100-100-p-103-iso10646-1
-adobe-helvetica-bold-o-normal--20-140-100-100-p-103-iso8859-1
-adobe-helvetica-bold-o-normal--25-180-100-100-p-138-iso10646-1
-adobe-helvetica-bold-o-normal--25-180-100-100-p-138-iso8859-1
-adobe-helvetica-bold-o-normal--34-240-100-100-p-182-iso10646-1
-adobe-helvetica-bold-o-normal--34-240-100-100-p-182-iso8859-1

lists no 12 point fonts at all.

The program generating the warning is XEmacs, but I don't believe this is an XEmacs problem as the app was able to find the font in question earlier today, before my ill-fated attempt to upgrade to Fedora 33 Workstation. Clearly the needed font is not known to the server for some reason.

For completeness, my current OS is SL 7.9 (again).

Any advice would be appreciated.