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 similar condition have had auction prices that vary, but are generally lower than those in better condition.

2. Auction History: By observing the hammer prices of coins with a similar condition (70) in the past, we can see that they have reached hammer prices ranging from 12 to 35 euros, depending on demand and other factors.

3. Average Hammer Price: The average hammer price for this particular coin is 84.28 euros, but this includes coins of different conditions. For a condition of 70, the hammer price is likely to be lower.

4. Recent Trends: In the most recent auctions, hammer prices for coins with similar conditions have been in the range of 30 to 50 euros.

5. Starting Price: The starting price is 12 euros, which suggests that the auction house expects moderate interest in the coin.

Taking all these factors into account, an estimated maximum purchase price for this coin, considering its condition and price history, could be in the range of 40 to 60 euros. This would allow for competitive bidding in the auction without exceeding the expected market value for a coin in this state of preservation.