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 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 observing previous hammer prices for coins with similar conditions (80 and 85), we can see that the hammer price has varied. For example:
- In previous auctions, coins with a condition of 80 have reached hammer prices of up to 150 euros.
- The coin with a condition of 85 has reached hammer prices of up to 270 euros.

3. Average Hammer Price: The average hammer price for this coin is 86.06 euros, providing a reference point.

4. Starting Price: The starting price is 50 euros, suggesting that the auctioneer expects interest in the coin.

5. Recent Trends: In the most recent auctions, hammer prices for coins of similar condition have shown an increase, which could indicate a rising trend in interest for these coins.

Based on these factors, an estimated maximum purchase price for this coin could be between 120 and 150 euros, considering that the condition is good and there is a history of hammer prices that supports this estimate. However, it is important to keep in mind that the final price will depend on the competition in the auction and the interest of other bidders.