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 is an important factor, as coins in better condition tend to reach higher prices.

2. Previous Auction Prices: By observing previous auction prices for coins with similar conditions (in this case, most coins with conditions of 80 and 85), we can see that auction prices have varied. For example, in recent auctions, the hammer prices for coins with a condition of 80 have reached up to 380 euros and 420 euros.

3. Starting Price and Average Hammer Price: The current starting price is 250 euros, and the average hammer price in the past has been 288.28 euros. This suggests that the hammer price could be in a similar range or slightly higher.

4. Auction Trends: The coin has been auctioned 27 times, of which 26 have sold. This indicates good demand and consistent interest in the coin.

5. Comparison with Estimated Prices: The estimated prices in previous auctions for coins with similar conditions have been up to 350 euros.

Taking all these factors into account, an estimated maximum purchase price for the coin with a condition of 70 (VF-) could be in the range of 350 to 400 euros. This is based on the trend of previous hammer prices and the condition of the coin.