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 75 (MBC), indicating that it is in quite good shape. This generally increases its value compared to coins with lower conditions.

2. Current Starting Price and Previous Prices: The current starting price is 350 euros. In previous auctions, hammer prices have varied, but the average hammer price is 314.29 euros. This suggests that the current starting price is slightly higher than the average of what has been sold in the past.

3. Price Trends: Looking at previous hammer prices, there has been an increase in prices in recent auctions, especially in 2024, where hammer prices have reached up to 420 euros for coins of similar condition.

4. Supply and Demand: The coin has been auctioned 9 times in the past, of which it has sold 7 times. This indicates good demand, which may justify a higher price.

Based on these factors, an estimated maximum purchase price could be positioned between the starting price and the highest observed hammer price. Given that the highest hammer price in the past was 420 euros and considering the current condition, a reasonable maximum purchase price could be approximately 400 euros. This reflects a balance between the condition, price trends, and demand observed in previous auctions.