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

1. Current Condition: The coin has a condition rating of 85 (MS+/EF-), indicating that it is in relatively good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Starting Price and Average Hammer Price: The starting price is 170 euros, and the average hammer price in previous auctions is 160.38 euros. This suggests that the starting price is reasonable and that the coin has a history of sales in a similar range.

3. Sales History: In the past, the coin has had hammer prices that varied, but there are examples of auctions where prices exceeded 200 euros, especially in similar conditions. For instance, in recent auctions, hammer prices of 200 euros and more have been seen for coins with comparable conditions.

4. Recent Trends: In the most recent auctions, hammer prices have shown a trend of increasing, which could indicate growing interest in this coin.

Based on these factors, an estimated maximum purchase price could be in the range of 200 to 250 euros, considering that the condition is good and there is a history of hammer prices that supports this estimate. However, since the starting price is 170 euros, it may be prudent to start bidding in that range and adjust according to the competition in the auction.