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-), indicating that it is in relatively good condition. This suggests that its value should be in the upper range of coins with similar grades.

2. Previous Prices: By looking at previous auction prices for coins with a grade of 70, we can see that:
- In 2018, a coin with a grade of 70 was auctioned for a hammer price of 15 euros.
- In 2022, another coin with a grade of 70 sold for 35 euros.
- In 2023, a coin with a grade of 80 sold for 170 euros, indicating that the value can increase significantly with better condition.

3. Average Hammer Price: The average hammer price for this coin is 90.3 euros, which also suggests that there is a higher selling potential.

4. Auction Trends: The coin has been auctioned 12 times, of which 10 have sold. This indicates good demand and consistent interest in the coin.

5. Starting Price: The starting price is 25 euros, which is relatively low compared to previous hammer prices.

Based on these factors, an estimated maximum purchase price could be in the range of 70 to 100 euros, considering that the condition is 70 and there are precedents for sales in that range. However, given the interest and demand, a reasonable maximum purchase price could be 90 euros.