To estimate a maximum purchase price for the coin in question, we will consider several factors:

1. Condition: The coin has a condition of 80 (MS+), which indicates that it is in quite good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Auction history:
- In the June 2021 auction, a coin with a condition of 80 sold for 80 euros, which is a significant price.
- In the November 2020 auction, a coin with a condition of 70 sold for 40 euros, suggesting that condition has a considerable impact on price.

3. Starting price and previous prices:
- The current starting price is 35 euros, which is reasonable given the price history.
- The average hammer price in the past has been 60 euros, which is also a good indicator.

4. Demand and supply: Since there are no auctions scheduled in the coming days, this could increase competition among bidders, potentially driving up the price.

Taking all these factors into account, an estimated maximum purchase price could be around 80-90 euros, given that it is the highest recorded price for a coin of similar condition and considering the good condition of the current coin. However, it is important to remember that the final price may vary depending on competition in the auction and other market factors.