To estimate a maximum purchase price for the coin with a grade of 70 (MS-), we can analyze historical data from previous auctions and consider several factors:

1. Grade: The coin in question has a grade of 70, which is a medium-high quality level. In the past, coins with a similar grade have had auction prices that vary, but they generally fall within a significant range.

2. Previous auction prices: By observing the auction prices of coins with a grade of 70, we find that:
- In several auctions, the hammer prices have been around 22, 40, 35, 30, and 25 euros.
- The average hammer price for coins of similar grade seems to be in the range of 25 to 40 euros.

3. Price trends: It is also important to consider that the average hammer price for this particular coin is 72.34 euros, indicating that there is potential for an increase in the hammer price, especially if demand is high.

4. Estimated price: In previous auctions, the estimated price for coins of similar grade has ranged from 14 to 90 euros, suggesting a wide range of price expectations.

5. Supply and demand analysis: Given that there is a scheduled auction and the coin has been auctioned 47 times in the past, with a sell-through rate of 83% (39 out of 47), this indicates a consistent interest in the coin.

Based on these factors, an estimated maximum purchase price for the coin with a grade of 70 could be in the range of 60 to 80 euros. This range takes into account both the average hammer price and the price trends in previous auctions, as well as the quality of the coin's grade.