To estimate a maximum purchase price for the coin with a grade of 70 (MS-), we can analyze historical data from previous auctions of coins with a similar grade and their hammer prices.

1. Relevant data from previous auctions:
- The grade of 70 (MS-) has had hammer prices that vary, but we can observe some examples:
- In 2020, a coin with a grade of 70 had a hammer price of 25 euros.
- In 2019, another coin with a grade of 70 was sold for 240 euros.
- In 2022, a coin with a grade of 70 was sold for 25 euros.

2. Analysis of hammer prices:
- The hammer prices for coins with a grade of 70 have ranged between 25 and 240 euros in previous auctions. However, the highest price seems to be an exceptional case.

3. Average hammer price:
- The average hammer price for similar coins is approximately 119.88 euros, indicating that, in general, coins of this grade tend to sell for higher prices than the starting price.

4. Starting price and estimation:
- The starting price of the coin is 12 euros, which is quite low compared to previous hammer prices. Given that the average hammer price is significantly higher, we can estimate a maximum purchase price.

5. Final estimation:
- Considering all these factors, an estimated maximum purchase price for the coin with a grade of 70 (MS-) could be between 80 and 120 euros, based on the historical behavior of similar auctions.

Therefore, a reasonable maximum purchase price could be 100 euros.