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

1. Current Condition: The coin has a condition of 80 (MS+), indicating that it is in quite good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Auction History: By looking at previous hammer prices for coins with a similar condition (80), we can see that the hammer prices have varied. For example:
- In previous auctions, coins with a condition of 80 have reached hammer prices of 25, 50, 100, and even 160 euros.
- The average hammer price for coins of similar condition is approximately 73.76 euros.

3. Starting Price and Average Starting Price: The current starting price is 35 euros, and the average starting price in the past has been 40.68 euros. This suggests that the current starting price is reasonable and could attract bidders.

4. Recent Trends: In the most recent auctions, hammer prices for coins in condition 80 have shown a range that can reach up to 150 euros, depending on demand and other factors.

Based on these points, an estimated maximum purchase price for this coin could be in the range of 100 to 150 euros. This is based on the historical hammer prices for coins of similar condition and the price trends in recent auctions. However, the final price will depend on the competition in the auction and the interest of collectors.