Display:

$C\text{|}$

Source:

<semantics>
     <mrow>
          <mpadded width="0">
               <mi> C </mi>
          </mpadded>
          <mspace width="0.3em"/>
          <mtext> | </mtext>
     </mrow>
     <annotation-xml encoding="MathML-Presentation">
          <mi> &Copf; </mi>
     </annotation-xml>
</semantics>