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 generally translates to a higher price compared to coins with lower conditions.

2. Previous Prices: By looking at previous auction prices, we can see that in the most recent auction (2023), the coin sold for 1800 euros, suggesting that there is significant interest in this coin in its current state.

3. Starting Price and Average Hammer Price: The current starting price is 1500 euros, and the average hammer price in previous auctions is 1230 euros. This indicates that the starting price is higher than the average hammer price, which may be an indicator that the seller expects greater interest in this auction.

4. Sales Trend: The coin has sold every time it has been auctioned, suggesting that there is consistent demand.

Based on these factors, an estimated maximum purchase price could be positioned in a range between the highest previous hammer price (1800 euros) and a bit more, considering the good condition and interest in the coin.

Therefore, an estimated maximum purchase price could be approximately 1900 to 2000 euros. This would allow for competitive bidding in the auction without exceeding a reasonable limit based on the sales history and current condition.