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 is 72.48 euros.
- The last auction for a coin with the same condition (80) had a hammer price of 135 euros.
- Overall, hammer prices have varied, but there are examples of coins with similar conditions that have sold for prices exceeding 100 euros.

3. Starting Price and Estimated Price:
- The current starting price is 60 euros, which is reasonable given the price history.
- The estimated price is 110 euros, suggesting expectations for the coin to reach a higher price.

4. Sales Trends: The coin has been sold in 21 of the last 23 auctions, indicating good demand.

Based on these factors, an estimated maximum purchase price could be in the range of 100 to 135 euros, considering that the highest hammer price in the past for a coin of similar condition was 135 euros.

Therefore, a reasonable maximum purchase price could be 130 euros. This allows for some margin for competition in the auction, given that the starting price is 60 euros and the estimated price is 110 euros.