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 80 (MBC+), which indicates that it is in relatively good shape. This generally translates to a higher price compared to coins in lower condition.

2. Current starting price and previous prices: The current starting price is 40 euros, and the average starting price in previous auctions is 70.45 euros, with an average hammer price of 87.24 euros. This suggests that the coin has a higher selling potential than its current starting price.

3. Auction history: The coin has been auctioned 26 times, of which it has sold 13 times. This indicates a moderate interest in the coin. Additionally, previous hammer prices varied, but there are examples of hammer prices exceeding 100 euros, especially for coins in better condition.

4. Price trends: Looking at previous hammer prices, there are examples of coins in similar condition that have sold for prices ranging from 90 to 150 euros.

Taking all these factors into account, an estimated maximum purchase price for this coin could be in the range of 90 to 110 euros, considering that the interest in the coin and its condition are favorable. Therefore, a reasonable maximum purchase price could be 100 euros.