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

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

2. Historical Prices: By looking at previous auction prices for coins with similar grades, we can see that:
- In 2019, a coin with a grade of 70 sold for 160 euros.
- In 2020, a coin with a grade of 80 sold for 290 euros.
- In 2022, a coin with a grade of 75 sold for 655 euros.

3. Average Auction Price: The average auction price for this coin is 364.14 euros, indicating that, in general, coins of this reference tend to sell for relatively high prices.

4. Starting Price: The current starting price is 125 euros, which may indicate a low initial price compared to previous auction prices.

5. Market Trends: Given that there has been an increase in auction prices in recent years, it is reasonable to assume that interest in this coin may be on the rise.

Based on these factors, an estimated maximum purchase price for the coin could be between 300 and 400 euros, considering that the grade is a limiting factor and that the highest auction price for a similar grade was 360 euros. Therefore, a reasonable maximum purchase price could be approximately 350 euros.