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

1. Coin Condition: The coin has a condition rating of 70 (MS-), indicating that it is in quite good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Auction History:
- The average hammer price for coins with a similar condition (70) in the past has been 40.7 euros.
- In previous auctions, hammer prices for coins with a condition of 70 have varied, but there have been hammer prices of up to 60 euros in recent auctions.

3. Starting Price and Previous Prices:
- The current starting price is 12 euros, which is relatively low compared to previous hammer prices.
- The average starting price in the past has been 27.41 euros, suggesting that the current starting price could be a good buying opportunity.

4. Price Trends:
- In recent auctions, hammer prices have shown a trend of increasing, especially for coins in good condition.

Based on these factors, an estimated maximum purchase price for this coin could be between 50 and 60 euros, considering that the average hammer price for coins with similar conditions has been 40.7 euros and that there is potential for the hammer price to reach higher figures depending on demand and collector interest.

Therefore, a reasonable maximum purchase price could be 55 euros.