Based on the data provided, we can observe that the coin has had an average auction closing price of 100.5 euros in previous auctions. Additionally, the current condition of the coin is 70 (VF-).

Considering that the current condition of the coin is relatively good and that the average auction closing price in previous auctions has been 100.5 euros, we could estimate a maximum purchase price around that value or slightly higher, taking into account the upward trend in closing prices.

Therefore, an estimated maximum purchase price for this coin in the upcoming auction could be around 105-110 euros. It is important to note that this is just an estimate and the final price could vary depending on demand at the auction and other external factors.