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

1. Coin Condition: The coin to be auctioned has a condition rating of 95 (EBC+), indicating that it is in very good condition. This generally increases its value compared to coins with lower conditions.

2. Auction History:
- The average hammer price for this coin in the past has been 21.71 euros.
- In previous auctions, hammer prices have varied significantly, with some reaching up to 65 euros for a condition rating of 100.
- The last auction with a similar condition (95) had a hammer price of 15 euros.

3. Starting Price and Estimates:
- The current starting price is 10 euros, and the average starting price in the past has been 11.06 euros.
- The estimated price for this auction is 15 euros, suggesting that bidders may be willing to pay more.

4. Sales Trends: The coin has been sold in 31 out of the last 34 auctions, indicating good demand.

Based on these factors, an estimated maximum purchase price could be in the range of 25 to 30 euros, considering that the condition is high and that the price history shows that coins in similar conditions have reached higher prices in the past.

Therefore, a reasonable maximum purchase price could be 30 euros.