To estimate a maximum purchase price for the coin in question, we can consider several factors based on the provided data:

1. Coin Condition: The coin being auctioned has a condition rating of 95 (EBC+), indicating that it is in very good condition. This generally translates to a higher price compared to coins with lower conditions.

2. Starting Price and Previous Prices: The current starting price is 90 euros. In previous auctions, the hammer prices for coins with similar conditions (95) have varied, but the highest hammer price for a coin with a condition of 95 was 100 euros.

3. Price Trends: The average hammer price for similar coins has been 55.25 euros, but given that this coin has a higher condition, it is reasonable to expect that the hammer price will be above this average.

4. Auction History: The coin has been auctioned 19 times, of which 17 have sold. This suggests good demand and sustained interest in the coin.

5. Previous Estimates: In past auctions, the estimated price for coins with a condition of 95 has been up to 100 euros, indicating that this could be a good reference point.

Considering all these factors, an estimated maximum purchase price for this coin could be between 100 and 120 euros, taking into account the high condition and the price history that supports this estimate. However, since the starting price is 90 euros, a realistic hammer price could be closer to 100 euros, but it should not exceed 120 euros in a competitive scenario.