To estimate a maximum purchase price for the coin in question, we can analyze the provided data, including auction history and previous hammer prices.

1. Current Grade: The coin has a grade of 70 (MS-). This is an important factor, as coins in better condition tend to achieve higher prices.

2. Price History:
- The average hammer price for coins of similar grade (70) in the past has been approximately 1000 euros.
- In previous auctions, hammer prices for coins with a grade of 70 have ranged between 900 and 1300 euros, depending on demand and other factors.

3. Starting Price: The starting price of 1500 euros is higher than the historical average hammer price, suggesting that the seller has high expectations. However, the starting price does not always translate into a successful hammer price.

4. Recent Trends: In the most recent auctions, hammer prices have shown a trend of being in the range of 1000 to 1300 euros for coins of similar grade.

5. Estimation: Given that the coin's grade is 70 and considering the price history, a reasonable maximum purchase price could be in the range of 1100 to 1300 euros. This is based on the fact that buyers are often willing to pay a little more than the average hammer price to secure a coin in good condition.

Therefore, an estimated maximum purchase price for this coin could be 1300 euros.