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. Starting Price and Average Hammer Price: The starting price is 75 euros, and the average hammer price in previous auctions is 73.87 euros. This suggests that the hammer price tends to be close to the starting price.

3. Price History: By looking at previous hammer prices for coins with a similar condition (80), we can see that they have reached hammer prices of up to 300 euros in the past (as in the auction on 2018-10-17). However, most hammer prices for condition 80 have been in a lower range, typically between 55 and 130 euros.

4. Recent Trends: In the most recent auctions, hammer prices for coins with a condition of 80 have been in the range of 100 to 150 euros, indicating that there is healthy demand for coins in this condition.

5. Competition Analysis: Since there are no scheduled auctions in the coming days for this coin, there may be less competition, which could allow the hammer price to be higher.

Based on these factors, an estimated maximum purchase price for this coin could be between 120 and 150 euros, considering that the condition is good and there is a price history that supports this estimate. However, it is important to note that the final price may vary depending on demand at the time of the auction.