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

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

2. Starting Price and Average Hammer Price: The current starting price is 35 euros, and the average hammer price in previous auctions is 53.86 euros. This suggests that, on average, similar coins have reached higher prices than the starting price.

3. Auction History: In the auction history, it is noted that in 2022, a coin with a condition of 80 was auctioned for 40 euros. This can serve as a reference point.

4. Price Trends: In the past, coins with similar conditions have reached hammer prices that varied, but generally, the hammer prices have been higher than the starting price.

5. Analysis of Previous Prices: By observing the hammer prices of coins with conditions ranging from 75 to 90, it can be inferred that the hammer price could be in a range of 40 to 75 euros, depending on demand and other market factors.

Based on these points, an estimated maximum purchase price for the coin in question could be between 50 and 70 euros, considering that the condition is good and that the price history suggests it could reach a higher price than the starting price.

Therefore, a reasonable estimated maximum purchase price could be 65 euros.