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

1. Condition: The coin has a condition rating of 75 (MBC), which is quite good. In the past, coins with a similar condition have reached auction prices ranging from 310 to 650 euros.

2. Auction History: The coin has been auctioned 17 times, of which 13 have been sales. This indicates a consistent interest in the coin. The average hammer price in previous auctions is 460 euros, providing a good reference point.

3. Starting and Hammer Prices: The current starting price is 300 euros, which is a reasonable price. However, the average starting price in the past has been 428.13 euros, suggesting there may be room for a higher hammer price.

4. Recent Trends: In the last auction, the coin sold for 300 euros, indicating that interest may be fluctuating. However, in previous auctions, it has reached higher prices, especially in similar conditions.

Taking all these factors into account, an estimated maximum purchase price could be around 500-600 euros. This is based on the auction price history for coins with a similar condition and the demonstrated interest in previous auctions.