I believe there may be an typo error in the mintage shown for this PROOF coin.
Listing shows it as 1,051,000. I believe it to be 1,051 as this proof set included 5p, 10p, 20p, and 50p all with a mintage of 1,051.
The 10 centavo, 50 centavo, and the Onza, also included in this set, had a mintage of 998.