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 75 (VF), indicating that it is in quite good shape. This generally increases its value compared to coins in lower condition.

2. Auction History:
- It has been auctioned 3 times in the past, of which it has sold 2 times. This suggests that there is interest in the coin, which may positively influence its price.
- The average hammer price in previous auctions is 75 euros, which sets a benchmark.

3. Current Starting Price: The starting price is 100 euros, indicating that the seller expects a higher price than the previous average hammer price.

4. Previous Prices:
- In the April 2021 auction, the coin was estimated at 60 euros and sold for 75 euros, suggesting that the market is willing to pay a bit more than the estimated price.
- In the February 2022 auction, the starting price was 25 euros, but the estimated price was 40 euros, indicating that interest may have increased since then.

5. Market Trends: Given that the average starting price has risen to 100 euros, this may reflect an increase in demand or perceived value of the coin.

Based on these factors, an estimated maximum purchase price could be positioned between the previous average hammer price (75 euros) and the current starting price (100 euros). Given that the condition is good and there is a history of sales, a reasonable maximum price could be approximately 90 euros. This allows for some competition in the auction while also staying below the starting price to avoid overpaying.