Based on the data provided, we can observe that the coin in question has had an average auction closing price of 19.25 euros in previous auctions. Additionally, its condition has been described as 70 (VF+), indicating that it is in an acceptable but not excellent condition.

Considering that the starting price of the upcoming auction is 12 euros and the historical average closing price has been 19.25 euros, we could estimate a maximum purchase price around 20-22 euros, taking into account the coin's condition and previous price history.

It is important to note that the final auction price may vary depending on the demand at that specific moment, so it is advisable to monitor the auction's progress to adjust the offer accordingly.