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 Condition: The coin has a condition 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 with a similar condition (70) has been approximately 185.84 euros.
- In previous auctions, hammer prices for coins with condition 70 have varied, reaching up to 220 euros on some occasions.

3. Recent Trends:
- In the most recent auctions, hammer prices have been in the range of 170 to 220 euros for coins with condition 70.
- The most recent auction with condition 70 had a hammer price of 170 euros.

4. Starting Price: The current starting price is 175 euros, indicating that the seller has expectations of a hammer price in that range.

5. Estimation: Given that the average hammer price for coins with condition 70 is 185.84 euros and considering that previous auctions have reached prices of up to 220 euros, an estimated maximum purchase price could be in the range of 200 to 220 euros, depending on the competition in the auction and the interest of collectors.

Conclusion: An estimated maximum purchase price for this coin could be 200 euros. This allows for a margin to compete in the auction without exceeding historical hammer prices.