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

1. Coin Condition: The coin has a condition rating of 30 (BC+), indicating that it is not in the best condition. This will affect its value compared to coins in better condition.

2. Auction History: The coin has been auctioned 77 times, of which it has sold 69 times. This suggests there is consistent interest in the coin, although the non-sale rate (8 times) also indicates that the desired price is not always reached.

3. Starting and Hammer Prices: The current starting price is 20 euros, and the average hammer price in the past has been 58.22 euros. This suggests that, on average, similar coins have achieved a significantly higher value than their starting price.

4. Previous Prices: Looking at the hammer prices of coins with similar conditions (around 30-40), prices have varied, but some have reached up to 90 euros in similar conditions.

5. Recent Trends: In the most recent auctions, hammer prices have shown a range that may indicate an increase in interest or value for the coin.

Based on these factors, an estimated maximum purchase price for this coin could be between 40 and 60 euros, considering that the average hammer price is 58.22 euros and that the condition is not optimal. A price of 50 euros could be a reasonable target, as it falls in the middle of this range and takes the condition into account.