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 85 (ebc-), indicating that it is in quite good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Auction History:
- The average hammer price for similar coins in the past is 89.33 euros.
- The last auction of a coin with a similar condition (85) had a hammer price of 220 euros in 2018, suggesting that there is a market willing to pay higher prices for coins in good condition.

3. Starting Price and Average Starting Price:
- The current starting price is 120 euros, which is higher than the average starting price of 58.75 euros. This may indicate that the seller has higher expectations due to the coin's condition.

4. Sales Trends: The coin has been auctioned 17 times, of which 15 have sold. This suggests that there is consistent interest in this coin, which may influence the price.

5. Comparison with Previous Prices:
- Previous hammer prices for coins with similar conditions (80-85) have varied, but the highest recorded price was 220 euros.

Based on these factors, an estimated maximum purchase price could be in the range of 150 to 200 euros, considering that the condition is good and there is a history of hammer prices that supports this estimate. However, given the starting price of 120 euros, it may be reasonable to consider a maximum purchase price around 180 euros, which is a midpoint between the starting price and the higher hammer prices observed in the past.