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. Coins with a higher condition tend to reach higher prices at auctions.

2. Sales History: The coin has been auctioned 79 times, of which 74 have been successful sales. This suggests that there is a consistent interest in this coin.

3. Previous Hammer Prices: By observing previous hammer prices, we can see that coins with similar conditions have reached varying hammer prices. For example:
- A coin with a condition of 85 sold for 255 euros.
- Another with a condition of 95 sold for 370 euros.
- A coin with a condition of 80 sold for 220 euros.

4. Average Hammer Price: The average hammer price for this coin is 338.79 euros, indicating that, in general, buyers are willing to pay close to this amount.

5. Starting Price: The starting price is 250 euros, which is a good starting point for the auction.

Given that the coin's condition is 70 (VF-), and considering the hammer price history of coins with similar conditions, an estimated maximum purchase price could be between 250 and 300 euros. This is based on the fact that, although the condition is not the highest, the interest in the coin and the sales history suggest that it could reach a reasonable price.

Therefore, an estimated maximum purchase price could be approximately 300 euros.