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 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 has been 52.19 euros.
- In previous auctions, we have seen hammer prices that varied depending on the condition. For example, in auctions with a condition of 85, hammer prices have reached up to 130 euros.
- The last auction of a coin with a similar condition (80) had a hammer price of 60 euros.

3. Starting Price and Average Starting Price:
- The current starting price is 25 euros, which is relatively low compared to the average hammer price.
- The average starting price of 34.84 euros also suggests that there is potential for an increase in the hammer price.

4. Sales Trends: The coin has been sold in 22 out of the 29 previous auctions, indicating good demand.

Based on these factors, an estimated maximum purchase price could be in the range of 60 to 80 euros, considering that the condition is good and that the hammer price history for coins of similar condition has been favorable.

Therefore, a reasonable maximum purchase price could be 70 euros.