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

1. Current Condition: The coin has a grade of 70 (MS-), indicating that it is in an acceptable state, but not among the best qualities.

2. Historical Prices: By looking at previous auction prices for coins with a similar grade (70), we can see that the hammer price has varied. For example:
- In a 2020 auction, a coin with a grade of 70 sold for 18 euros.
- In another auction in 2023, it sold for 20 euros.

3. Average Hammer Price: The average hammer price for this particular coin is 114.55 euros, but this includes coins of different grades. For higher grades, prices can be significantly higher.

4. Starting Price and Estimates: The starting price is 15 euros, and the average starting price is 59.77 euros. This suggests that the market expects the coin could reach a higher price.

5. Recent Trends: In the most recent auctions, hammer prices for coins with similar grades have been in the range of 20 to 40 euros.

Based on these factors, an estimated maximum purchase price for the coin with a grade of 70 could be between 25 and 40 euros, considering that the market may be willing to pay a bit more for a coin in an acceptable state.

Therefore, a reasonable maximum purchase price could be 35 euros.