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

1. Current Condition: The coin has a condition of 75 (MBC), which indicates that it is in relatively good shape. This is important because the price of coins tends to increase with better condition.

2. Auction History:
- The average hammer price in previous auctions is 132.28 euros.
- The coin has been auctioned 21 times, of which it has sold 19 times, indicating good demand.
- Previous hammer prices for coins with similar conditions (75 and 85) have varied, but there are examples of auctions reaching up to 140 euros.

3. Starting Price and Estimates:
- The current starting price is 25 euros, which is quite low compared to the average hammer price.
- The average starting price in previous auctions is 48 euros, suggesting that the current starting price could be a good buying opportunity.

4. Price Trends:
- In previous auctions, coins with conditions of 75 and 85 have reached hammer prices of up to 140 euros. This suggests that, although the starting price is low, the potential hammer price could be considerably higher.

Based on these factors, an estimated maximum purchase price could be in the range of 100 to 140 euros, considering that the condition is good and that the hammer price history supports this estimate. A price of 120 euros could be a reasonable target, as it falls in the middle of this range and reflects the price trend in previous auctions.