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 will affect its value.

2. Auction History:
- The average hammer price for similar coins in the past has been 86.58 euros.
- The condition of the coins auctioned in the past varied, but there are examples of coins with similar conditions that have sold for prices ranging from 9 to 40 euros, depending on the condition and demand.

3. Previous Hammer Prices:
- In previous auctions, coins with condition ratings of 30 have had hammer prices ranging from 9 to 40 euros.
- The most recent auction of a coin with a similar condition had a hammer price of 30 euros.

4. Market Trends: Given that the coin has been auctioned 91 times and has had a high sales percentage (82 out of 91), this suggests that there is a consistent interest in this coin.

Based on these factors, an estimated maximum purchase price for this coin could be in the range of 30 to 40 euros. This is based on the historical hammer prices for coins with a similar condition and the general interest in the coin. However, since the condition is not high, it is wise not to exceed 40 euros in the bid.