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

1. Current Condition: The coin has a condition of 85 (MBC+/EBC-), indicating that it is in quite good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Current Starting Price and Previous Prices: The current starting price is 250 euros. In previous auctions, the average hammer price has been 170.54 euros, but there are also examples of higher hammer prices, such as 240 euros in recent auctions.

3. Price Trends: By observing the hammer prices of coins with similar conditions (around 80-85), it can be noted that prices have fluctuated, but there seems to be a range between 170 and 300 euros, depending on demand and condition.

4. Sales History: The coin has been auctioned 40 times, of which 39 have sold. This indicates good demand and sustained interest in the coin.

5. Previous Estimates: In past auctions, price estimates have reached up to 500 euros in optimal conditions. However, given that the current condition is 85, it is more reasonable to expect a hammer price in a more conservative range.

Based on these factors, an estimated maximum purchase price could be between 250 and 300 euros, considering that the starting price is 250 euros and that the condition is quite good. This also takes into account the possibility that demand in the auction may be high, which could push the price towards the upper end of this range.