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

1. Current Condition: The coin has a condition rating of 90 (EF), indicating that it is in quite good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Auction History:
- The average hammer price for similar coins in the past is 6150.08 euros.
- The last auction of a coin with a condition of 95 reached a hammer price of 30000 euros, indicating a strong market for high-quality coins.
- Previous auctions with conditions of 85 and 90 have had hammer prices that varied, but overall, the prices have been quite competitive.

3. Starting Price and Average Starting Price:
- The current starting price is 3500 euros, which is above the average starting price of 2792.86 euros. This suggests that the seller is confident that the coin will fetch a good price.

4. Market Trends: Given that the coin has sold in the past within a price range that varies considerably, and considering that there has been an increase in hammer prices at recent auctions, it is reasonable to assume that interest in this coin may be high.

Based on these factors, an estimated maximum purchase price could be in the range of 7000 to 8000 euros. This is based on the average hammer price and the condition of the coin, as well as the trend of increasing hammer prices in recent auctions.