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

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. Historical Auction Data:
- The average hammer price for similar coins in the past has been 86.89 euros.
- The coin has been auctioned 163 times, of which it has sold 142 times, indicating good demand.
- Previous hammer prices for coins with a similar condition (30) have varied, but there are examples of auctions reaching up to 65 euros.

3. Starting Price and Estimates:
- The starting price is 40 euros, and the average starting price for similar coins is 55.58 euros.
- The estimated price for this coin is 60 euros, suggesting it could reach a hammer price close to this value.

4. Price Trends: Observing the hammer prices of coins with similar conditions, the range seems to be between 50 and 65 euros.

Based on these factors, an estimated maximum purchase price for this coin could be around 65 euros, considering that it reflects both the condition and historical demand. However, since the coin is not in optimal condition, it is wise not to exceed this value.