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 (MBC), which indicates that it is in quite good shape. This generally translates to a higher price compared to coins in lower condition.

2. Auction History:
- The average hammer price for this coin in the past is 40.29 euros.
- The condition of coins auctioned in the past varies, but there are examples of coins with similar condition (80) that have sold for 75 euros.
- The most recent auction with a condition of 85 had a starting price of 40 euros, suggesting that coins in better condition can reach higher prices.

3. Starting Price and Previous Prices:
- The current starting price is 20 euros, which is reasonable given the hammer price history.
- The trend of hammer prices for coins with similar condition suggests that the price could be in the range of 50 to 75 euros, depending on demand at the auction.

Taking all these factors into account, an estimated maximum purchase price for this coin could be around 60-70 euros. This is based on the hammer price history and the current condition of the coin.