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. Starting Price and Average Hammer Price: The starting price is 120 euros, and the average hammer price in previous auctions is 155.96 euros. This suggests that, in general, coins of this reference tend to sell for above their starting price.

3. Sales History: The coin has been auctioned 59 times, of which 56 have been sold. This indicates a high sales rate, which can be a good indicator of demand.

4. Previous Prices: By looking at the hammer prices of coins with similar grades (70-75), we can see that they have reached hammer prices that varied, but some have reached 130-190 euros in the past.

5. Recent Trends: In the most recent auctions, hammer prices have been in the range of 125 to 190 euros for coins with similar grades.

Based on these factors, an estimated maximum purchase price for this coin could be in the range of 160 to 190 euros, considering that the average hammer price is 155.96 euros and that the grade is a key factor. Therefore, a reasonable maximum purchase price could be 180 euros.