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), indicating that it is in relatively good shape, but not among the best qualities.

2. Auction History:
- The average hammer price for similar coins in the past is 294.66 euros.
- The condition of the coins that have been sold in the past varies, but there are examples of coins with higher conditions (90 and 95) that have sold for significantly higher prices (up to 550 euros).

3. Price Trends:
- In previous auctions, coins with similar conditions (80 and 90) have had hammer prices ranging from 80 to 550 euros, depending on demand and the specific quality of the coin.

4. Starting Price: The starting price of 20 euros is quite low compared to the average hammer price, suggesting that there could be considerable room for bidding.

5. Sale Expectations: Given that it has sold in the past within a considerable price range, and considering the current condition, a reasonable hammer price could be in the range of 150 to 300 euros.

### Estimated Maximum Purchase Price
Taking all these factors into account, an estimated maximum purchase price for this coin could be around 250 euros. This price reflects a balance between the current condition, the auction price history, and the general market trend.