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

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. Auction History:
- The average hammer price for similar coins in the past is 54.26 euros.
- The average starting price is 39.65 euros.
- In previous auctions, hammer prices have varied, but there are examples of sales reaching up to 96 euros (as in the auction on October 27, 2020).

3. Current Starting Price: The starting price is 100 euros, indicating that the seller has high expectations for this auction.

4. Price Trends: Observing previous hammer prices, it seems there is a price range that varies depending on the condition and demand at the time of the auction. Coins with similar conditions have reached hammer prices of up to 80-90 euros in the past.

Given all this, an estimated maximum purchase price could be set in a range between 80 and 100 euros, considering that the condition is good and there is a history of hammer prices supporting this figure. However, since the starting price is 100 euros, it might be reasonable to consider a maximum purchase price of around 90 euros, assuming that competition in the auction is not too high.