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 780 euros. In previous auctions, we have seen hammer prices that varied, but there are recent examples where coins with similar conditions have reached hammer prices of up to 1100 euros.

3. Price Trends: The average hammer price for this coin in the past has been approximately 673.02 euros, but there are examples where they have sold above this average, especially in higher conditions.

4. Comparison with Previous Sales: In recent auctions, coins with condition ratings of 80 have reached hammer prices ranging from 700 to 925 euros. The trend seems to indicate a growing interest in coins of good condition.

5. Market Expectations: Given that there are no auctions scheduled in the coming days and considering the number of times this coin has sold (68 out of 79 auctions), there is sustained interest in this reference.

Based on these factors, an estimated maximum purchase price for this coin could be between 900 and 1100 euros, considering that the interest in coins of good condition may lead bidders to compete for it. A hammer price of around 950 euros could be a reasonable target, given the current market context and the condition of the coin.