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

1. Current Condition: The coin is in a condition of 90 (EBC), indicating that it is in good shape. This generally translates to a higher price compared to coins in lower conditions.

2. Auction History:
- The average hammer price in previous auctions is 13.89 euros.
- The coin has been auctioned 26 times, of which it has sold 18 times, indicating good demand.
- Previous hammer prices varied, but there are examples of auctions reaching up to 45 euros in similar conditions.

3. Starting Price and Estimates:
- The current starting price is 8 euros, and the average starting price in the past has been 8.69 euros.
- The estimated price for this auction is 15 euros, suggesting expectations of an increase in the hammer price.

4. Recent Trends: In the most recent auctions, hammer prices have shown an increase, which may indicate a positive trend in the coin's value.

Taking all these factors into account, an estimated maximum purchase price could be around 20-25 euros, considering that the condition is good and there is a history of hammer prices supporting this figure. However, it is important to be aware of the competition in the auction, as this may influence the final price.

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

1. Current Condition: The coin has a condition rating of 25 (BC), indicating that it is not in very good shape. This generally reduces its value compared to coins in better condition.

2. Auction History:
- The average hammer price for similar coins in the past has been 51.22 euros.
- Previous auctions show that coins with similar conditions (some with a condition rating of 30) have reached hammer prices of up to 33 euros.
- The most recent auction of a coin with a condition rating of 30 had a hammer price of 30 euros.

3. Starting Price and Previous Sales:
- The current starting price is 10 euros, which is relatively low and may attract more bidders.
- The sell-through rate in previous auctions is high (18 out of 20), suggesting there is consistent interest in this coin.

4. Price Trends:
- The average starting price of 39.9 euros and the average hammer price of 51.22 euros indicate that, in general, bidders are willing to pay more than the starting price.

Taking all these factors into account, an estimated maximum purchase price for this coin could be around 30-35 euros. This is based on the hammer price history for coins of similar condition and the demonstrated interest in previous auctions.

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

1. Current Condition: The coin has a condition rating of 80 (MBC+). This is an important factor, as coins in better condition tend to fetch higher prices.

2. Auction History:
- The average hammer price for similar coins in the past is 33.5 euros.
- The condition of the coins auctioned in the past varies, but there are examples of coins with similar conditions (80) that have sold for prices ranging from 15 to 25 euros.

3. Starting and Estimated Prices:
- The current starting price is 12 euros, and the average starting price in the past has been 23.43 euros.
- The estimated price for this auction is 20 euros, suggesting that there are expectations for the coin to sell for a reasonable price.

4. Sales Trends: Of the 27 times it has been auctioned in the past, it has sold 21 times, indicating a good sales rate.

5. Comparison with Previous Prices:
- In previous auctions, coins with similar conditions have reached hammer prices of up to 30 euros or more, depending on demand and condition.

Based on these factors, a maximum estimated purchase price for this coin could be between 25 and 35 euros, considering that the condition is good and there is a history of hammer prices that supports this estimate.

Therefore, a reasonable maximum purchase price could be 30 euros.

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

1. Current Grade: The coin has a grade of 70 (MS-). This is an important factor, as coins in better condition tend to reach higher prices.

2. Auction History:
- The average hammer price for coins of similar grade (70) in the past has been approximately 52.02 euros.
- In previous auctions, coins with a grade of 70 have reached hammer prices of up to 65 euros (as seen in the auction on September 19, 2019).

3. Starting Price and Average Starting Price:
- The current starting price is 12 euros, which is quite low compared to the average starting price of 31.39 euros.
- This suggests that there is potential for the hammer price to be significantly higher.

4. Recent Trends:
- In the most recent auctions, hammer prices for coins of similar grade have varied, but they have shown a range that can reach up to 60-70 euros in some cases.

5. Data-Based Estimation:
- Given that the average hammer price for coins of grade 70 is 52.02 euros and considering that there is a history of hammer prices reaching up to 65 euros, an estimated maximum purchase price could be in the range of 60 to 70 euros.

Conclusion: Based on the analysis of the data, an estimated maximum purchase price for this coin could be 65 euros. This is based on the history of hammer prices and the current grade of the coin.