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

1. Current Condition: The coin has a condition of 80 (MS+), indicating that it is in quite good shape. This suggests that its value should be above that of coins with lower conditions.

2. Historical Prices: By looking at the auction prices of coins with a similar condition (80), we can see that they have reached auction prices that vary, but some examples are:
- 170 euros (condition 85)
- 63 euros (condition 85)
- 80 euros (condition 80)
- 36 euros (condition 80)

3. Average Auction Price: The average auction price for similar coins is 119.88 euros, indicating that there is a market willing to pay higher prices for coins in good condition.

4. Starting Price: The starting price of 35 euros is relatively low compared to previous auction prices, suggesting that there could be a good buying opportunity.

5. Recent Trends: The price trend in recent auctions shows that coins with similar conditions have performed well, which could indicate an increase in demand.

Based on these factors, an estimated maximum purchase price for this coin could be in the range of 100 to 150 euros. This is based on the current condition, previous auction prices, and market interest. However, it is important to note that the final price may vary depending on competition in the auction and specific demand at the time of sale.