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

1. Current Condition: The coin has a condition of 75 (VF), which indicates that it is in relatively good shape, but not among the best qualities.

2. Auction History:
- The coin has been auctioned 7 times, of which it has sold 6 times. This indicates a consistent interest in the coin.
- Previous hammer prices varied, but there are examples of hammer prices of 1800 euros (in 2019) and 950 euros (in 2021) for conditions of 90 and 95, respectively.

3. Average Starting and Hammer Price:
- The average starting price is 983.33 euros and the average hammer price is 1137.5 euros. This suggests that, in general, coins of this reference tend to sell above their starting price.

4. Comparison with Previous Prices:
- In previous auctions, the coin has reached hammer prices of up to 1800 euros, but it has also had lower hammer prices, such as 800 euros.

Given that the current condition is 75 (VF), which is lower than the conditions of 90 and 95 that reached higher prices, and considering the average hammer price, an estimated maximum purchase price could be set in a more conservative range.

Estimated Maximum Purchase Price:
We could estimate a maximum purchase price around 900-1100 euros, taking into account the condition and price history. This would allow for competitive bidding in the auction without exceeding the market value seen in previous auctions for coins in better condition.