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

1. Current Condition: The coin has a condition of 85 (ebc-), which indicates that it is in fairly good shape, but not the best possible condition.

2. Auction History:
- The average hammer price in previous auctions is 48.17 euros.
- In past auctions, coins with a similar condition (85) have had hammer prices that vary, but some examples are:
- 2020-09-17: Hammer price 45 euros (condition 85).
- 2022-04-28: Hammer price 20 euros (condition 85).
- 2023-03-22: Hammer price 25 euros (condition 85).

3. Starting Price and Average Starting Price:
- The current starting price is 20 euros, and the average starting price in previous auctions is 27.75 euros.

4. Sales Trends: The coin has been auctioned 35 times, of which it has sold 23 times, indicating a reasonable sales rate.

Based on this data, an estimated maximum purchase price could be positioned in a range between the average hammer price and the highest hammer price observed for coins with a similar condition.

Given that the average hammer price is 48.17 euros and considering that the condition is 85, a reasonable maximum purchase price could be:

Estimated maximum purchase price: 50 euros.

This price reflects a balance between the condition, price history, and sales trend.