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

1. Current Condition: The coin has a condition rating of 85 (ebc-), indicating that it is in quite good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Starting Price and Average Hammer Price: The starting price is 90 euros, and the average hammer price in previous auctions is 98.6 euros. This suggests that, in general, coins of this reference tend to sell for above their starting price.

3. Sales History: The coin has been auctioned 24 times, of which 20 have resulted in sales. This indicates good demand and consistent interest in this coin.

4. Previous Prices: Looking at previous hammer prices, the highest recorded price was 340 euros in an auction in 2018, although this was for a coin with a condition of 95. However, there are also lower hammer prices ranging from 45-100 euros for coins with lower conditions.

5. Recent Trends: In the most recent auctions, hammer prices have varied, but the average hammer price of 98.6 euros suggests that buyers are willing to pay close to this value.

Taking all these factors into account, an estimated maximum purchase price for this coin could be around 120-130 euros. This is based on the good condition of the coin, the price history, and the trend of hammer prices in previous auctions.