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 85 (MBC+/EBC-), indicating that it is in quite good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Current Starting Price and Previous Prices: The current starting price is 90 euros. In previous auctions, the average hammer price has been 70.03 euros, suggesting that the market has valued this coin at a range lower than the current starting price.

3. Historical Trends: Looking at the hammer prices from previous auctions, there are examples of similar coins that have sold for prices that varied significantly. For instance, in 2018, a coin with a condition of 95 sold for 300 euros, while others with a condition of 70-80 sold for between 40 and 75 euros.

4. Supply and Demand: The coin has been auctioned 91 times, with 82 sales, indicating good demand. However, there are 2 auctions scheduled in the coming days, which could affect competition and the final price.

5. Estimated Maximum Price: Given that the condition is relatively high and considering the starting price and previous hammer prices, a reasonable maximum purchase price could be in the range of 100 to 120 euros. This is based on the idea that collectors might be willing to pay a bit more for a coin in good condition, but also taking into account that the average hammer price has been lower than the starting price.

Therefore, an estimated maximum purchase price for this coin could be 110 euros.