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

1. Current Condition: The coin has a condition rating of 75 (MBC), indicating that it is in quite good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Auction History:
- The average hammer price in previous auctions is 52.58 euros.
- The coin has been auctioned 20 times, of which it has sold 13 times, indicating good demand.
- Previous hammer prices for coins with similar conditions (70-85) have varied, but there are examples of auctions reaching up to 130 euros.

3. Starting Price and Average Starting Price:
- The current starting price is 25 euros, and the average starting price in the past has been 32.16 euros. This suggests that the current starting price is reasonable.

4. Price Trends:
- In previous auctions, hammer prices have shown a considerable range, with some reaching high prices in similar conditions.

Based on these factors, an estimated maximum purchase price could be in the range of 70 to 100 euros, considering that the condition is good and there is a history of hammer prices supporting this estimate. A more conservative price could be around 80 euros, while a more optimistic price could reach 100 euros, depending on the competition in the auction.

Therefore, a reasonable estimated maximum purchase price would be 80-100 euros.