To estimate a maximum purchase price for the coin in question, we can analyze the provided data:

1. Condition: The coin has a condition of 70 (VF-), indicating that it is in relatively good shape. This may positively influence its price.

2. Auction History:
- The average hammer price in previous auctions is 19.27 euros.
- In auctions where the coin has been sold with a similar condition (70), the hammer prices have varied, but there are examples where prices have reached up to 30 euros (such as in the auction on 2022-07-14).

3. Starting and Hammer Prices:
- The current starting price is 12 euros, which is lower than the historical average hammer price.
- The average starting price in previous auctions is 15.27 euros, suggesting that the current starting price is competitive.

4. Price Trends:
- In previous auctions, hammer prices have ranged between 12 and 30 euros for coins with similar conditions.

Based on this data, an estimated maximum purchase price could be set in a range between 25 and 30 euros, considering that the condition is good and that the price history shows that hammer prices have reached that range. Therefore, a reasonable maximum purchase price could be 30 euros.