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

1. Current Condition: The coin has a grade of 70 (MS-). This indicates that it is in an acceptable state, but it is not of the highest quality.

2. Historical Prices: By looking at the auction prices of coins with similar grades (70-80), we can see that the auction prices have varied. For example:
- In 2019, a coin with a grade of 70 sold for 141 euros.
- In 2020, another coin with a grade of 70 sold for 240 euros.
- In 2022, a coin with a grade of 75 sold for 340 euros.

3. Average Auction Price: The average auction price for this coin is 417.69 euros, suggesting that, in general, coins of this reference tend to reach higher prices.

4. Starting Price: The starting price is 175 euros, which could be a good starting point for the auction.

5. Recent Trends: In recent auctions, the hammer prices have shown an increase, especially for coins in similar conditions.

Based on these factors, an estimated maximum purchase price could be between 250 and 350 euros, considering that the grade is 70 and that the auction prices for similar grades have varied within that range. This also takes into account the average auction price and the potential interest from other collectors.