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

1. Current Condition: The coin has a condition of 85 (MS+/EF-), indicating that it is in fairly good shape, but not the best possible condition.

2. Historical Prices: By looking at previous auction prices for coins with similar conditions, we can see that:
- In past auctions, coins with conditions ranging from 80 to 95 have had hammer prices that varied significantly, from 38 euros to 600 euros.
- The average hammer price for coins with similar conditions (around 85) seems to be in the range of 150 to 300 euros.

3. Starting Price and Average Hammer Price: The current starting price is 75 euros, and the average hammer price in the past has been 151.23 euros. This suggests that the hammer price could be significantly higher than the starting price.

4. Auction Trends: Given that the coin has been auctioned 35 times in the past and has had a sell-through rate of 88.57% (31 out of 35), this indicates relatively high 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 good and there is a history of hammer prices that supports this estimate.

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