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

1. Condition: The coin has a condition rating of 80 (MS+), indicating that it is in relatively good shape. This is important because coins in better condition tend to fetch higher prices.

2. Auction History:
- It has been auctioned 5 times in the past, of which it sold 3 times.
- The average hammer price in previous auctions is 786.67 euros, suggesting that there is significant interest in this coin.
- In past auctions, hammer prices have varied considerably, with a hammer price of 1800 euros for coins with a condition rating of 95.

3. Current Starting Price: The starting price is 60 euros, which is quite low compared to the historical average hammer price.

4. Comparison with Previous Prices: The last auction with a condition rating of 80 had a hammer price that is not specified, but there is a hammer price of 60 euros for a coin with a condition rating of 10, indicating that the price could be significantly higher for a condition rating of 80.

Given all this, an estimated maximum purchase price could be in a range that considers historical interest and the current condition.

Estimation: We could estimate a maximum purchase price around 500-600 euros, considering that the average hammer price is 786.67 euros and that the condition of this coin is better than some of those that have sold in the past. However, since the starting price is 60 euros, it is likely that competition in the auction could drive the price higher, but it may not necessarily reach the historical average due to the difference in condition.