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 95 (EF+), indicating that it is in very good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Previous Prices: By looking at previous auction prices for coins with the same condition (95), we can see that they have reached auction prices that vary but are generally in a high range. For example, in recent auctions, the hammer prices have been between 270 and 380 euros.

3. Starting Price and Average Hammer Price: The current starting price is 300 euros, and the average hammer price in the past has been approximately 257.92 euros. However, given that the condition is high and there is a trend for hammer prices to be higher in recent auctions, we can expect the hammer price to be above average.

4. Market Trends: The coin has been auctioned 66 times, with a high sales percentage (61 out of 66). This suggests that there is consistent interest in this coin, which may increase its value.

5. Previous Price Estimates: In previous auctions, the estimated price has been up to 400 euros, indicating that there is potential for the hammer price to be high.

Taking all these factors into account, an estimated maximum purchase price for this coin could be around 380-400 euros. This is based on the trend of previous hammer prices and the high condition of the coin.