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. Previous Auction Prices: By looking at previous auction prices for coins with similar grades, we can see that:
- Coins with a grade of 70 have had auction prices that vary, but generally range between 100 and 150 euros.
- For example, in previous auctions, coins with a grade of 70 have reached hammer prices of 130 euros and 140 euros.

3. Average Hammer Price: The average hammer price for this coin is 146.93 euros, suggesting that, in general, buyers are willing to pay close to this price.

4. Starting Price: The starting price is 120 euros, which is a good starting point for the auction.

5. Recent Trends: In the most recent auctions, hammer prices have been in the range of 150 to 170 euros for similar grades.

Based on these factors, an estimated maximum purchase price for this coin could be between 150 and 170 euros, considering that the condition is an important factor and that interest in the coin may influence the final price.

Therefore, a reasonable maximum purchase price could be 160 euros.