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

1. Current Condition: The coin has a condition rating of 80 (MBC+), indicating that it is in quite good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Auction History:
- The coin has been auctioned 16 times, of which it has sold 12 times. This suggests there is consistent interest in the coin.
- The average hammer price in previous auctions is 32.9 euros, which can serve as a benchmark.
- Looking at the hammer prices from previous auctions for coins with similar conditions (75-85), prices have varied between 21 and 45 euros.

3. Starting Price and Estimates:
- The current starting price is 40 euros, which is slightly higher than the previous average hammer price. However, the estimated price of 50 euros in the most recent auction suggests there is potential for a higher hammer price.

4. Recent Trends: In the most recent auctions, hammer prices for coins with similar conditions have been in the range of 30 to 45 euros.

Based on these factors, an estimated maximum purchase price could be in the range of 45 to 55 euros, considering that the condition is good and there is interest in the coin. Therefore, a reasonable maximum purchase price could be 50 euros.