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

1. Current Condition: The coin has a condition rating of 75 (VF), indicating a medium-low quality. This can influence the price, as coins in better condition tend to fetch higher prices.

2. Auction History:
- The average hammer price for similar coins in the past has been 237.65 euros.
- In previous auctions, we have seen hammer prices that varied significantly, from 44 euros to 1200 euros, depending on the condition and other factors.
- The last auction of a similar coin with a condition rating of 85 reached a hammer price of 300 euros, suggesting that there is an active market for coins of similar quality.

3. Starting Price and Average Starting Price:
- The current starting price is 75 euros, and the average starting price in the past has been 131.19 euros. This suggests that the current starting price is relatively low compared to the historical average.

4. Sales Trends: The coin has been sold in 20 out of the 22 previous auctions, indicating good demand.

Based on these factors, an estimated maximum purchase price could be in the range of 200 to 300 euros, considering that the condition is a limiting factor and that the average hammer price in the past has been significantly higher.

Therefore, a reasonable maximum purchase price could be 250 euros.