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

1. Current Condition: The coin has a condition rating of 70 (MBC-). This is an important factor, as coins in better condition tend to reach higher prices.

2. Auction History:
- The average hammer price for similar coins has been 66.56 euros.
- In previous auctions, we have seen hammer prices that varied significantly, from 9 euros to 250 euros, depending on the condition and other factors.

3. Starting Price and Average Starting Price:
- The current starting price is 40 euros, and the average starting price in the past has been 45.65 euros.

4. Price Trends:
- In recent auctions, coins with a similar condition (70) have reached hammer prices of up to 100 euros (as seen in the auction on June 21, 2021).

5. Analysis of Previous Prices:
- The most recent auction with a condition of 70 had a hammer price of 60 euros.

Based on this data, an estimated maximum purchase price for this coin could be in the range of 70 to 100 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 80 euros. This allows for a margin for competition in the auction, given that the hammer price may vary depending on demand at the time of the auction.