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. Current Listing Price and Previous Prices: The current listing price is 70 euros. In previous auctions, we have seen hammer prices that varied significantly, but there are examples of similar coins that have sold for significantly higher prices, especially those with a similar or better condition.

3. Price Trends: The average hammer price for similar coins is 84.45 euros, suggesting that the hammer price could be in a similar or higher range, depending on the demand at the auction.

4. Sales History: The coin has been auctioned 103 times, with an 85% sell-through rate, indicating a consistent interest in this coin. This may influence competition during the auction.

5. Recent Hammer Prices: In recent auctions, we have seen hammer prices reaching up to 850 euros for coins in better condition. However, for coins with a condition of 80, hammer prices have been closer to 100-150 euros in some cases.

Based on these factors, an estimated maximum purchase price for this coin could be between 100 and 120 euros, considering that the condition is good and there is a history of hammer prices that supports this estimate. However, if there is strong competition at the auction, the price could exceed this estimate.