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

1. Condition: The coin has a condition rating of 75 (VF), which indicates that it is in fairly good shape, but not the best possible condition. This may influence the price, as coins in better condition tend to fetch higher prices.

2. Auction History:
- In the past, this coin has been auctioned 5 times, of which it has sold 4 times. This indicates a consistent interest in the coin.
- Previous hammer prices vary, but the highest was 1100 euros in a recent auction with a condition of 90. This suggests that there is an active market and that prices can fluctuate significantly depending on condition and demand.

3. Starting Price and Average Prices:
- The current starting price is 100 euros, which is relatively low compared to the average hammer price of 465 euros. This suggests that there could be considerable room for the hammer price to be higher than the starting price.

4. Comparison with Previous Prices:
- The average hammer price in previous auctions is 465 euros, which can serve as a good indicator of the current market value.

Taking all these factors into account, an estimated maximum purchase price could be in the range of 400 to 600 euros, considering that the condition is slightly lower than that of the highest auction and that the starting price is low. A hammer price of around 500 euros could be a reasonable target, given the sales history and current condition.