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 75 (MBC), 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 76.7 euros.
- It has been auctioned 25 times, of which 21 have sold, indicating good demand.
- Previous hammer prices for coins with similar conditions (around 75) have varied, but there are examples of auctions reaching up to 400 euros in exceptional conditions.

3. Starting Price and Average Starting Price:
- The current starting price is 15 euros, which is quite low compared to the average starting price of 40.64 euros. This suggests that there may be a buying opportunity at a favorable price.

4. Recent Trends: In the most recent auctions, hammer prices have ranged from 50 to 190 euros, which also indicates potential for an increase in the hammer price.

Based on these factors, an estimated maximum purchase price for this coin could be in the range of 100 to 150 euros. This range takes into account the good condition of the coin, historical demand, and recent hammer prices.