To estimate a maximum purchase price for the coin in question, we can analyze the provided data, especially the previous auction prices and the current condition of the coin.

1. Current Condition: The coin has a condition of 80 (MBC+). This is an important factor, as coins in better condition tend to achieve higher prices at auctions.

2. Previous Auction Prices: By observing the auction prices of coins with a similar condition (80) in the past, we can see that:
- In several auctions, coins with a condition of 80 have reached hammer prices ranging from 180 to 600 euros.
- For example, in previous auctions, the hammer prices for coins with a condition of 80 have been: 240, 220, 190, 340, 320, 360, etc.

3. Average Hammer Price: The average hammer price for this coin is 421.82 euros, indicating that, in general, coins of this reference tend to sell for relatively high prices.

4. Starting Price: The starting price is 175 euros, suggesting that the seller expects a lower price initially, but this does not necessarily reflect the true value of the coin.

5. Auction Trends: Given that the coin has been auctioned 53 times and has had a high sales percentage (50 out of 53), this indicates a consistent interest in this coin.

### Estimation of Maximum Purchase Price
Taking all these factors into account, an estimated maximum purchase price for this coin could be in the range of 400 to 600 euros, considering that the condition is good and that previous hammer prices have reached similar figures.

Therefore, a reasonable maximum purchase price could be approximately 500 euros. This is based on the trend of previous hammer prices and the current condition of the coin.