Michael Norrish <Michael.Norrish@nicta.com.au> writes:

> The following text (featuring character U+1D54C), doesn't display the
> SMP char
>
>   ``𝕌(:num) ≼ 𝕌(:'a ucinf)``,
>
> even after doing
>
>   (set-fontset-font t 'unicode-smp "STIXGeneral")
>
> The character viewer on the Mac confirms that this font is in the system
> and has a glyph for that character code.

This looks like it's working fine in Emacs 25: