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

1. Current Condition: The coin has a condition rating 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. Starting Price and Average Hammer Price: The starting price is 75 euros, and the average hammer price in previous auctions is 84.11 euros. This suggests that, on average, similar coins have reached prices above the starting price.

3. Sales History: The coin has been auctioned 67 times, of which it has sold 63 times. This indicates good demand and a history of successful sales.

4. Previous Prices: Looking at previous hammer prices for coins with a similar condition (80), we find that they have reached prices of up to 190 euros (in the case of an auction in 2018). However, most hammer prices for similar conditions are in the range of 80 to 120 euros.

5. Recent Trends: In the most recent auctions, hammer prices have been in the range of 80 to 120 euros, suggesting that interest in this coin remains steady.

Based on these factors, an estimated maximum purchase price for this coin could be between 100 and 120 euros, considering that the condition is good and there is a history of hammer prices that supports this estimate.

Therefore, a reasonable maximum purchase price could be 120 euros.