To estimate a maximum purchase price for the coin in question, we will consider several factors:

1. Current Condition: The coin has a condition rating of 75 (VF), indicating that it is in acceptable shape, but not among the best conditions. This will affect its value compared to coins in better condition.

2. Auction History:
- The average hammer price in previous auctions is 1075 euros, suggesting that, in general, coins of this reference tend to sell for relatively high prices.
- The last auction with a known hammer price was 750 euros for a coin with the same condition (75) in 2022.

3. Starting Price and Average Starting Price:
- The current starting price is 400 euros, which is below the average starting price of 520 euros. This could indicate a buying opportunity, but it may also reflect lower demand at this time.

4. Price Trends:
- In previous auctions, hammer prices have varied significantly, ranging from 250 euros to 2000 euros, depending on condition and other factors.

Based on this data, an estimated maximum purchase price could be set in a range that considers the average hammer price and the current condition. Given that the condition is 75 and the average hammer price is 1075 euros, a reasonable maximum purchase price could be:

Estimated maximum purchase price: 900 - 1100 euros.

This range allows for competitive bidding in the auction without exceeding the historical value of the coin in similar conditions.