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 a medium-low state. This may influence the price, as coins in better condition tend to fetch higher prices.

2. Starting Price and Hammer Price: The current starting price is 80 euros, and the average hammer price in previous auctions is 137.01 euros. This suggests that, in general, coins of this reference tend to sell for a price higher than the starting price.

3. Auction History: In the auction history, we have seen hammer prices that vary significantly. For example, in 2013, a coin with the same condition sold for 72.91 euros, while another in better condition (90) reached 260 euros. This indicates that the price can fluctuate depending on demand and condition.

4. Recent Trends: In more recent auctions, hammer prices have ranged from 76 to 220 euros, suggesting that there is ongoing interest in this coin.

5. Average Hammer Prices: Given that the average hammer price is 137.01 euros, this can serve as a good indicator of what could be expected.

Taking all these factors into account, an estimated maximum purchase price for this coin could be in the range of 120 to 150 euros. This is based on the average hammer price and the current condition. However, since the condition is 75, it is likely that the actual hammer price will be closer to the lower end of this range.

Therefore, a reasonable maximum purchase price could be 130 euros.