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

2. Current Listing Price and Previous Prices: The current listing price is 85 euros, and the average hammer price in previous auctions has been 72.7 euros. However, there have been auctions where higher hammer prices were reached, such as 130 euros in a previous auction.

3. Price Trends: Looking at previous hammer prices, there is a trend where coins of similar condition have reached hammer prices that vary, but some have exceeded 100 euros. For example, in 2021, a coin with a condition of 80 was sold for 110 euros.

4. Demand and Supply: Since this coin has sold every time it has been auctioned (23 times), this suggests that there is a consistent demand for this reference.

Based on these factors, an estimated maximum purchase price could be in the range of 100 to 130 euros, considering that the condition is good and there are precedents of high hammer prices in previous auctions.

Therefore, a reasonable maximum purchase price could be 120 euros.