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 (MBC+/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 has been 104.75 euros.
- In previous auctions, hammer prices have ranged from 25 euros to 320 euros, depending on condition and other factors.

3. Starting Price and Estimated Price:
- The current starting price is 75 euros, which is reasonable given the price history.
- The estimated price of 300 euros in a previous auction (2021) for a coin with a similar condition (85) suggests there is significant potential for a higher hammer price.

4. Sales Trends: The coin has been sold in 13 out of the last 15 auctions, indicating good demand.

Based on these factors, an estimated maximum purchase price could be in the range of 150 to 200 euros. This is based on the hammer price history and the current condition of the coin. However, since the starting price is 75 euros, it is likely that the actual hammer price will be closer to the lower end of this range unless there is significant competition in the auction.

Therefore, a reasonable maximum purchase price could be 200 euros.