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 70 (VF-). This indicates that it is in an acceptable state, but not of high quality.

2. Historical Prices: By looking at previous auction prices for coins with a similar condition (70-75), we can see that auction prices have varied. For example, in past auctions, coins with a condition of 75 have reached hammer prices of up to 400 euros.

3. Starting Price and Average Price: The current starting price is 140 euros, and the average hammer price in the past has been 406.31 euros. This suggests that there is significant potential for the hammer price to be higher than the starting price.

4. Market Trends: Since the coin has been auctioned 656 times and has had a high number of sales (573), this indicates a constant interest in this coin, which may influence the price.

5. Comparison with Prices of Similar Condition: In the past, coins with a condition of 70 have had hammer prices ranging from 150 to 300 euros, depending on demand and other factors.

Based on these points, an estimated maximum purchase price for this coin could be between 250 and 350 euros, considering the interest in the coin and its current condition. This allows for a margin for competition in the auction, but also remains within a reasonable range based on historical data.