To estimate a maximum purchase price for the coin in question, we can analyze 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. Historical Prices: By looking at previous auction prices for coins with a similar condition (80), we can see that auction prices have varied, but there are examples where hammer prices have reached up to 600 euros (such as in the auction on October 17, 2018).

3. Average Hammer Price: The average hammer price for this coin is 308.5 euros, which provides a good reference for the expected value.

4. Starting Price: The current starting price is 175 euros, which is below the average hammer price, suggesting that there may be a buying opportunity.

5. Recent Trends: In the most recent auctions, hammer prices have shown a trend of being higher, especially for coins in good condition.

Based on these factors, an estimated maximum purchase price could be in the range of 400 to 500 euros, considering that the coin is in good condition and there have been examples of high hammer prices in the past. This also takes into account the possibility that bidders may be willing to pay more in a competitive auction.