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 (MS+), indicating that it is in quite good shape. This generally translates to a higher price compared to coins in lower conditions.

2. Current Listing Price and Previous Prices: The current listing price is 40 euros, and the average hammer price in previous auctions is 37.28 euros. However, there have been previous auctions where the coin has sold for significantly higher prices, such as 154.69 euros in 2013.

3. Price Trends: Looking at the hammer prices from previous auctions, there is a trend where coins in similar conditions have reached hammer prices that vary considerably, but generally tend to be higher than the current listing price.

4. Demand and Supply: The coin has been auctioned 57 times, with 34 sales, indicating moderate interest. The lack of upcoming auctions may also influence demand.

Considering these factors, an estimated maximum purchase price could be in the range of 60 to 80 euros, given that the condition is good and there are precedents for higher prices in the past. A price of 75 euros could be a reasonable target, as it aligns with the average hammer price and the condition of the coin.