Mintage figures Numista/Marsh

[GuyL]

Does anyone know why the mintage figures for a 1991 Two Pound (Double Sovereign) Proof "T58" coin is 3108 in The Gold Sovereign Series book by Michael Marsh but only 620 on the Numista website entry?

It is quite a discrepancy; am I missing something?

[Arganto]

As far as I am aware Numista's entries are added by members as opposed to one group of people employed to do so. This means there will inevitably be errors, especially considering the vast size of their database (covering everything coin/medal/token shaped). Curating it must be something of a challenge. Their values are often way out also as they are based on averages that members declare, sometimes not being updated for huge periods of time. Although Marsh could/do make mistakes I would imagine 'The Gold Sovereign' is checked and proof read many times as a more specialised publication.