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 (MS+), indicating that it is in quite good shape. This generally translates to a higher price compared to coins with lower conditions.

2. Auction History:
- The average hammer price for similar coins in the past has been 63.13 euros.
- In previous auctions, the coin has reached hammer prices of up to 130 euros (in 2016) and has had several hammer prices in the range of 30 to 100 euros, depending on the condition and starting price.

3. Starting Price and Average Starting Price:
- The current starting price is 30 euros, which is relatively low compared to the average hammer price.
- The average starting price of 50.26 euros suggests that similar coins usually start auctioning at a higher price.

4. Recent Trends: In the most recent auctions, the coin has had hammer prices ranging from 33 to 100 euros, indicating a consistent interest in this type of coin.

Based on these factors, an estimated maximum purchase price could be in the range of 80 to 100 euros, considering the good condition and the hammer price history. This would allow for effective competition in the auction without exceeding the market value observed in previous auctions.

Therefore, an estimated maximum purchase price could be 100 euros.