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 75 (MBC), indicating that it is in quite good shape. This is important because coins in better condition tend to fetch higher prices.

2. Auction History:
- The average hammer price for similar coins has been 125.9 euros.
- In previous auctions, we have seen hammer prices that varied, but some have reached up to 320 euros under similar conditions (such as in the auction on 2021-06-22).

3. Starting Price and Average Starting Price:
- The current starting price is 40 euros, which is relatively low compared to the average hammer price.
- The average starting price has been 70 euros, suggesting that the market is willing to pay more than the starting price.

4. Sales Trends: The coin has been sold in 21 out of the last 22 auctions, indicating good demand.

5. Comparison with Previous Prices:
- In previous auctions, coins with a similar condition have reached hammer prices of 95 to 150 euros, and in some exceptional cases, up to 220 euros.

Based on these factors, an estimated maximum purchase price for this coin could be between 150 and 200 euros, considering that the condition is good and there is a history of hammer prices that supports this estimate. However, given the starting price of 40 euros, it could be a good opportunity to acquire it at a lower price if the competition in the auction is not high.