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

1. Starting price: 200 euros. This is the initial price set for the auction.
2. Auction history: The coin has been auctioned 4 times in the past, of which it has sold 3 times. This indicates that there is interest in the coin.
3. Average hammer price: 140 euros. This is the average price at which the coin has sold in previous auctions.
4. Condition: The coin has a condition rating of 80 (MBC+), indicating that it is in good condition, which may increase its value.
5. Previous prices: The previous hammer prices have been 140, 150, and 130 euros, suggesting that the value of the coin has fluctuated but has remained within a similar range.

Given that the condition of the coin is good (80), and considering the starting price of 200 euros, it is reasonable to think that the hammer price could be above the average of 140 euros, but it will not necessarily reach the starting price.

Taking all these factors into account, an estimated maximum purchase price could be between 160 and 180 euros. This reflects an increase over the average hammer price, but also considers that the starting price is higher and that the coin is in good condition.

Therefore, an estimated maximum purchase price could be 170 euros.

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 (MBC+), indicating that it is in relatively good shape, but not among the best qualities.

2. Starting Price: The starting price is 120 euros, which sets a baseline for the auction.

3. Sales History:
- The average hammer price in previous auctions is 128.77 euros.
- It has been auctioned 24 times, of which 15 have sold, indicating a sales rate of 62.5%. This suggests there is interest in the coin, but also that there is a 37.5% chance it has not sold, which may influence the perception of its value.

4. Previous Prices:
- In past auctions, hammer prices have varied significantly, ranging from 60 euros to 400 euros, depending on condition and other factors.
- The last auction with a hammer price of 400 euros was notably high, but there is no information on the condition of that coin.

5. Comparison with Similar Conditions:
- Coins with similar conditions (around 80) have had hammer prices ranging from 60 to 150 euros in the past.

Based on these factors, an estimated maximum purchase price could be in the range of 130 to 150 euros. This is based on the average hammer price and the condition of the coin. However, since the starting price is 120 euros, it is reasonable to consider that a hammer price around 140 euros could be a realistic target, assuming demand remains steady.

Therefore, an estimated maximum purchase price could be 140 euros.