= Solution
The equilibrium written in the reduction direction is
$$
\boxed{\mathrm{Ag_2SO_4(s)+2e^-\rightleftharpoons2Ag(s)+SO_4^{2-}(aq)}}.
$$
With pure-solid activities set to one, the <Nernst equation> gives
$$
\boxed{E_{\rm ref}=E^\circ_{\rm Ag_2SO_4/Ag}
-\frac{RT}{2F}\ln a_{\rm SO_4^{2-}}}.
$$
Maintaining sulfate activity fixes the reference potential; protonation to bisulfate in strongly acidic filling solutions must be included in specifying that activity.
Calibrate against, or use a reliable tabulated potential relative to, the <standard hydrogen electrode> for the \b[same filling solution and temperature]. With the voltmeter sign specified above and a corrected or negligible junction potential,
$$
\boxed{E_{\rm working\ vs\ SHE}=V_{\rm meas}+E_{\rm ref\ vs\ SHE}}.
$$
There is no universal numerical offset for every silver reference: silver/silver-chloride, silver/silver-sulfate and different sulfate filling solutions define different potentials.
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