To estimate a maximum purchase price for the coin that is going to be auctioned, we will consider several factors:

1. Condition of the coin: The coin in question has a condition rating of 90 (EF), which indicates that it is in quite good shape.

2. Previous auction prices: By looking at the hammer prices of coins with a similar condition (90) in previous auctions, we can see that the hammer prices have varied. For example, in recent auctions, coins with a condition of 90 have reached hammer prices ranging from 35 to 100 euros.

3. Average hammer price: The average hammer price for similar coins is approximately 98.9 euros.

4. Starting price: The starting price of the auction is 25 euros, which suggests that there is considerable room for the hammer price to be higher.

5. Market trends: Since the coin has been auctioned 1,295 times in the past and has had a high sales percentage (999 out of 1,295), this indicates a consistent demand.

Based on these factors, an estimated maximum purchase price for the coin could be in the range of 90 to 120 euros, considering that the condition is good and that the average hammer price in the past has been approximately 98.9 euros.

Therefore, a reasonable maximum purchase price could be 120 euros.