To estimate a maximum purchase price for the coin in question, we can analyze the provided data, especially the auction history and previous hammer prices.

1. Current Condition: The coin has a condition rating of 90 (EF), indicating that it is in good shape. This is a positive factor that can increase its value.

2. Price History:
- The average hammer price for this coin in the past is 1149.38 euros.
- In previous auctions, hammer prices have varied, but there are examples of sales exceeding 1000 euros, even reaching up to 1900 euros in an auction with a condition of 95.

3. Comparison with Starting Prices:
- The current starting price is 600 euros, which is slightly higher than the average starting price of 581.25 euros. However, the starting price does not always translate into the final hammer price.

4. Price Trends:
- The general trend shows that coins with a similar condition have reached hammer prices ranging between 850 and 1300 euros, depending on the condition and demand at the time of the auction.

5. Estimation:
- Given that the coin's condition is 90 and considering the hammer price history, an estimated maximum purchase price could be around 1200-1300 euros. This is based on the fact that the coin is in good condition and has performed solidly in previous auctions.

Therefore, an estimated maximum purchase price for this coin could be 1300 euros.