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

1. Current Condition: The coin has a condition rating of 80 (MS+), indicating that it is in quite good shape. This can positively influence its value.

2. Historical Prices:
- In previous auctions, the coin has had hammer prices that vary, but the highest was 2150 euros in 2024 with a condition of 85.
- The average hammer price in past auctions is 1444.5 euros, providing a good reference point.

3. Starting Price and Estimates:
- The current starting price is 1500 euros, which is above the average starting price of 1114.29 euros, suggesting that the seller has high expectations.
- The estimated hammer price for this auction is 1500 euros, which also indicates that considerable interest is expected.

4. Sales Trends: The coin has been auctioned 7 times, of which it has sold 4 times. This suggests that there is moderate interest in the coin, but also that it has not sold 43% of the time, which could indicate that the starting price is an important factor.

5. Comparison with Previous Prices:
- In previous auctions with similar condition (80), hammer prices have been around 1102 euros and 1300 euros. This suggests that the hammer price could be in a similar range.

Based on these factors, an estimated maximum purchase price could be between 1300 and 1600 euros. Given that the starting price is 1500 euros and considering the condition and historical prices, a reasonable maximum price could be 1600 euros. This would allow for competitive bidding in the auction without exceeding the starting price too much, taking into account the interest and quality of the coin.