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

1. Current Grade: The coin has a grade of 75 (MS), indicating that it is in quite good condition. This generally translates to a higher price compared to coins with lower grades.

2. Auction History: By looking at previous hammer prices for coins with similar grades, we can see that:
- In past auctions, coins with a grade of 75 have reached hammer prices of up to 110 euros.
- Coins with a grade of 70 have had hammer prices that varied, but some have reached 100 euros.

3. Average Hammer Price: The average hammer price for this coin is 106.73 euros, which also suggests that the hammer price may be in a high range.

4. Starting Price and Previous Prices: The current starting price is 40 euros, which is relatively low compared to previous hammer prices. This may indicate that there is potential for an increase in the hammer price.

Taking all these factors into account, an estimated maximum purchase price for this coin could be around 110-120 euros, given that it is a price that has been reached in previous auctions for coins of similar grade and considering the history of hammer prices.