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 30 (BC+). This indicates that it is not in the best condition, which generally affects its value.

2. Auction History:
- The average hammer price for similar coins in the past has been 73.76 euros.
- Previous auctions of coins with similar conditions (around 30) have had hammer prices that varied, but are generally lower than the overall average.

3. Recent Starting and Hammer Prices:
- In recent auctions, the hammer prices for coins with similar conditions have ranged from 20 to 30 euros, with some cases reaching up to 36 euros.

4. Market Trends: Since the coin has been auctioned 111 times and has had a high sales percentage (104 out of 111), this suggests there is consistent interest in this coin, which may influence its price.

5. Starting Price: The starting price is 12 euros, indicating that the seller has moderate expectations.

Based on these factors, an estimated maximum purchase price for this coin, considering its condition and price history, could be between 25 and 35 euros. This reflects a balance between market interest and the condition of the coin.