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

1. Condition of the coin: 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. Starting price and previous prices: The starting price of the auction is 90 euros. In the past, this coin has had hammer prices that varied, but some have reached up to 140 euros under similar conditions (as seen in the auction on September 15, 2022).

3. Price trends: The average hammer price in previous auctions is 60.13 euros, but there are examples of higher hammer prices, especially for coins in similar condition.

4. Supply and demand: The coin has been auctioned 30 times, of which 26 have sold. This suggests that there is a consistent interest in this coin, which may influence the price.

5. Estimated price: In previous auctions, the estimated price has varied, but it has reached up to 100 euros under similar conditions.

Taking all these factors into account, a maximum estimated purchase price could be in the range of 120 to 140 euros, given that the condition is high and there are precedents for hammer prices in that range. However, since the starting price is 90 euros, it is advisable not to exceed this limit unless there is strong competition in the auction.

Therefore, a reasonable maximum purchase price could be 130 euros.