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

1. Current Condition: The coin has a condition rating of 90 (EF), indicating that it is in quite good shape. This generally translates to a higher value compared to coins in lower conditions.

2. Auction History:
- The average hammer price for similar coins in the past is 40.39 euros.
- The last auction for this coin had a starting price of 75 euros and an estimated price of 100 euros, with a final hammer price of 80 euros in 2020.
- In previous auctions, hammer prices have varied, but there are examples of sales reaching up to 120 euros.

3. Price Trends:
- The overall trend seems to indicate that prices have been increasing, especially for coins in better condition.
- The coin has been auctioned 29 times, of which 25 have been sold, indicating a consistent interest in this coin.

4. Starting Price and Estimates:
- The current starting price is 75 euros, suggesting that the seller has expectations of a higher hammer price.
- Given that the average hammer price in the past has been 40.39 euros, but considering the condition and interest, it is reasonable to expect a higher final price.

Based on these factors, an estimated maximum purchase price could be between 100 and 120 euros, given the auction history and the good condition of the coin. This aligns with previous hammer prices and the estimated price of the last auction.