To estimate a maximum purchase price for the coin in question, let's consider several factors:

1. Condition of the coin: The coin to be auctioned has a condition rating of 100 (S/C), indicating that it is in very good shape. This generally translates to a higher price compared to coins with lower condition ratings.

2. Starting price and previous prices: The current starting price is 125 euros. In previous auctions, the average hammer price has been 144.85 euros, suggesting that coins of this reference tend to sell for above their starting price.

3. Auction history: The coin has been auctioned 64 times, of which 56 have sold. This indicates good demand and consistent interest in this coin. Additionally, the average hammer price in previous auctions has been 144.85 euros, reinforcing the idea that the selling price may exceed the starting price.

4. Previous estimated prices: In several previous auctions, estimated prices have been significantly higher than the starting prices. For example, in a 2020 auction, the estimated price was 180 euros, and the hammer price was 180 euros. This suggests that buyers are willing to pay higher prices for coins in good condition.

5. Recent trends: In the most recent auctions, hammer prices have ranged from 160 to 190 euros for coins of similar condition.

Taking all these factors into account, a maximum estimated purchase price for this coin could be between 180 and 200 euros. This is based on the good condition of the coin, the history of hammer prices, and the demand observed in previous auctions.

Therefore, a reasonable maximum purchase price could be 190 euros.