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 of 75 (MBC), indicating that it is in quite good shape. This can positively influence its price.

2. Auction History:
- It has been auctioned 8 times in the past, of which it has sold 5 times. This suggests there is consistent interest in the coin.
- The average starting price in previous auctions is 69.97 euros, and the average hammer price is 91.46 euros. This indicates that, on average, similar coins have reached hammer prices that exceed the starting price.

3. Previous Prices:
- In 2013, the coin sold for 122.09 euros, which is a notably high price.
- In 2014, with a condition of 75, the starting price was 50.56 euros, but no hammer price was reported.
- In 2015, it sold for 156.34 euros, which is also a high price.
- In 2017, the starting price was 75 euros, but no hammer price was reported.

4. Price Trends: Hammer prices have varied, but there are examples of high prices in the past, suggesting that the coin may have significant value in the market.

Based on these factors, an estimated maximum purchase price could be set in a range that considers both the average hammer price and the highest prices reached in previous auctions.

Given that the condition is good and there is a history of high prices, a reasonable maximum purchase price could be:

Estimated maximum purchase price: 130 - 150 euros.

This range takes into account the interest in the coin, its condition, and previous hammer prices.