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. Historical Prices: By looking at previous auction prices for coins with similar grades (70-85), we can see that auction prices have varied. For example:
- In previous auctions with a grade of 70, the hammer prices have been around 170-270 euros.
- For grades of 80 and 85, the hammer prices have been higher, reaching up to 950 euros in an exceptional case.

3. Average Hammer Price: The average hammer price for this coin is 344.85 euros, indicating that, in general, coins of this reference tend to sell for relatively high prices.

4. Starting Price and Average Starting Price: The current starting price is 125 euros, and the average starting price is 193 euros. This suggests that the current starting price is relatively low compared to the historical average.

5. Auction Trends: The coin has been auctioned 26 times, with a sell-through rate of 84.6% (22 out of 26). This indicates consistent demand.

Based on these factors, an estimated maximum purchase price could be in the range of 250 to 350 euros, considering that the grade is 70 and the average hammer price is 344.85 euros. However, since the starting price is 125 euros, it could be a good opportunity to acquire it at a lower price, as long as the competition in the auction is not high.

Therefore, a reasonable maximum purchase price could be 350 euros.