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

1. Current Condition: The coin has a condition of 70 (VF-). This is an important factor, as coins in better condition tend to reach higher prices.

2. Previous Prices: By observing the auction prices of coins with similar conditions, we can see that coins with conditions of 80 and 85 have reached auction prices of up to 440 euros. Coins with conditions of 90 and 95 have reached auction prices of up to 605 euros.

3. Average Auction Price: The average auction price for this coin is 303.63 euros, indicating that, in general, coins of this reference tend to sell around this price.

4. Starting Price: The starting price is 275 euros, suggesting that the seller expects a reasonable price based on previous auctions.

5. Auction Trends: The coin has been auctioned 55 times, of which 52 have been sold. This indicates good demand and a history of successful sales.

Based on these factors, an estimated maximum purchase price could be in the range of 350 to 400 euros. This is because, although the condition is 70, the auction price history and demand suggest it could reach a higher price than the average, but not as high as coins in better condition.

Therefore, a reasonable maximum purchase price could be 400 euros.