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 (EF-), 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 64.35 euros.
- In previous auctions, coins with a similar condition (85) have reached hammer prices that vary, but some have gone as high as 140 euros (as in the auction on September 15, 2022).

3. Starting Price and Estimated Price:
- The current starting price is 40 euros, which is reasonable given the history of starting and hammer prices.
- The estimated price for this auction is 70 euros, which also suggests potential for an increase in the hammer price.

4. Market Trends: Since the coin has been auctioned 33 times and has had a high sales percentage (30 out of 33), this indicates a consistent interest in the coin, which may influence an increase in the hammer price.

Based on these factors, an estimated maximum purchase price could be in the range of 80 to 100 euros. This is based on the hammer price history for coins of similar condition and the demonstrated interest in previous auctions.

Therefore, a reasonable maximum purchase price could be 90 euros.