To estimate a maximum purchase price for the coin in question, we can analyze the provided data and consider several factors:

1. Current Condition: The coin has a condition rating of 75 (VF), indicating that it is in quite good shape. This generally translates to a higher price compared to coins in lower conditions.

2. Auction History:
- The average hammer price for similar coins in the past is 508.89 euros.
- The coin has been auctioned 10 times, of which it has sold 9 times, indicating good demand.
- Previous hammer prices for coins with similar conditions (70-75) have varied, but the range seems to be between 160 and 350 euros in the most recent auctions.

3. Starting Price: The current starting price is 300 euros, which is a reasonable starting point.

4. Price Trends: Looking at previous hammer prices, it appears that coins with a condition of 70-75 have reached hammer prices ranging from 160 to 350 euros. However, since this coin's condition is 75, it is reasonable to expect that the hammer price will be at the upper end of this range.

5. Final Estimate: Considering all these factors, an estimated maximum purchase price could be around 400-450 euros. This is based on the good condition of the coin and the hammer price history for similar coins.

Therefore, an estimated maximum purchase price for this coin could be 450 euros.