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. Previous Auction Prices: By observing previous auction prices for coins with similar grades, we can see that:
- In 2018, a coin with a grade of 70 was auctioned for 55 euros.
- In 2022, a coin with a grade of 85 was auctioned for 120 euros.
- In 2023, a coin with a grade of 80 was auctioned for 190 euros.

3. Average Auction Price: The average auction price for this coin is 171.13 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 70 euros, and the average starting price is 97.42 euros. This suggests that the starting price is reasonable compared to the average.

5. Auction Trends: The coin has been auctioned 34 times, of which 32 have sold. This indicates good demand and consistent interest in this reference.

Based on these factors, an estimated maximum purchase price could be in the range of 150 to 200 euros, considering that the grade is slightly lower than some coins that have sold for higher prices, but there is still an auction history suggesting it could reach a significant price.

Therefore, an estimated maximum purchase price could be 180 euros.