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

1. Current Condition: The coin has a condition of 75 (MBC), which indicates that it is in an acceptable state, but not among the best qualities. This can influence the price, as coins in better condition tend to reach higher prices.

2. Previous Prices: By observing previous auction prices for coins with similar conditions, we can see that:
- In past auctions, coins with a condition of 75 have reached hammer prices of up to 320 euros.
- The last auction with a condition of 75 had a hammer price of 320 euros.

3. Average Hammer Price: The average hammer price for this coin is 348.4 euros, suggesting that, in general, coins of this reference tend to sell for higher prices.

4. Starting Price: The current starting price is 125 euros, which is relatively low compared to previous hammer prices.

5. Auction Trends: The coin has been auctioned 23 times, of which 20 have sold. This indicates good demand and consistent interest in the coin.

Taking all these factors into account, an estimated maximum purchase price for this coin could be around 300-350 euros, as this price reflects both the current condition and previous hammer prices, as well as the interest in the coin.

Therefore, a reasonable maximum purchase price could be 350 euros.