To estimate a maximum purchase price for the coin in question, we can consider 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. Auction History: By looking at previous hammer prices for coins with similar conditions, we can see that:
- In past auctions, coins with a condition of 75 have reached hammer prices of up to 65 euros.
- Coins with a condition of 80 have occasionally reached hammer prices of up to 120 euros.

3. Average Hammer Price: The average hammer price for this coin is 51.97 euros, providing a reference point.

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

5. Starting Price and Estimated Price: The starting price is 30 euros, and the estimated price is 50 euros. This suggests that the market expects considerable interest in this coin.

Taking all these factors into account, an estimated maximum purchase price for this coin could be between 80 and 120 euros, considering its good condition and the interest it has shown in previous auctions. A price of 100 euros could be a reasonable target for a competitive bid.