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

1. Current Condition: The coin is in a condition of 90 (EF), indicating that it is in quite good shape. This generally increases its value compared to coins in lower conditions.

2. Starting Price and Average Hammer Price: The starting price is 60 euros, and the average hammer price in previous auctions is 57.38 euros. This suggests that the starting price is reasonable and that, in general, coins of this reference tend to sell close to this price.

3. Sales History: The coin has been auctioned 26 times, of which 16 have resulted in sales. This indicates a consistent interest in the coin, which may influence its value.

4. Previous Prices: Looking at previous hammer prices, there are examples of prices that vary significantly, from 9 euros to 200 euros. However, the most recent and relevant prices are more indicative of the current value.

5. Market Trends: Given that the coin is in good condition and has a history of successful sales, it is reasonable to assume that it could reach a price above the starting price.

Taking all these factors into account, an estimated maximum purchase price could be between 80 and 100 euros. This is based on the good condition of the coin and the demonstrated interest in previous auctions. However, the final price will depend on the competition in the auction and the demand at the time of sale.