To estimate a maximum purchase price for the coin in question, we will consider several factors:

1. Condition: The coin has a condition rating of 80 (MS+), indicating that it is in quite good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Current listing price and previous prices: The current listing price is 750 euros. In previous auctions, we have seen hammer prices that varied significantly, but there are examples of coins with similar conditions that have sold for higher prices. For instance, at the March 2022 auction, a coin with a condition of 95 sold for 800 euros, and at another auction in March 2023, a coin with a condition of 95 sold for 1000 euros.

3. Price trends: The average hammer price for similar coins is 597.4 euros, but there are examples of sales that exceed this average, especially for coins in better condition.

4. Demand and supply: The coin has been auctioned 40 times in the past, with a sell-through rate of 92.5% (37 out of 40). This suggests that there is consistent interest in this coin, which may increase its value at auction.

5. Proximity of the auction: Since it will be auctioned in the coming days, competition may be high, which could also influence the final price.

Taking all these factors into account, an estimated maximum purchase price could be between 900 and 1100 euros. This is based on the fact that, although the listing price is 750 euros, the coin's condition and previous price trends suggest it could reach a higher price at auction.