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

1. Current Condition: The coin has a condition 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 conditions, we can see that:
- In past auctions, coins with conditions of 70 have reached hammer prices of up to 110 euros.
- The average hammer price for coins with similar conditions seems to be around 66-90 euros.

3. Starting Price and Average Hammer Price: The starting price is 40 euros, and the average hammer price in the past has been 91.56 euros. This suggests there is potential for an increase in the hammer price.

4. Recent Trends: In the most recent auctions, the hammer price has varied, but it has reached figures close to 110 euros for coins in similar conditions.

Based on these factors, an estimated maximum purchase price for this coin could be between 90 and 110 euros, considering that the condition is good and there is a price history that supports this estimate.

Therefore, a reasonable maximum purchase price could be 100 euros.