To estimate a maximum purchase price for the coin in question, we will consider several factors:

1. Current Condition: The coin has a condition of 70 (MS-). This is an important factor, as coins in better condition tend to reach higher prices.

2. Auction History:
- The average hammer price for coins of similar condition (70) in the past has been approximately 70-110 euros, with some auctions reaching up to 220 euros in exceptional cases.
- The last auction of a coin with a condition of 70 had a hammer price of 110 euros.

3. Starting Price and Average Starting Price:
- The current starting price is 30 euros, which is quite low compared to the average hammer price of 102.89 euros.
- The average starting price of 55 euros also suggests that there is potential for an increase in the hammer price.

4. Sales Trends: The coin has been sold in 28 of the 36 previous auctions, indicating good demand.

5. Previous Prices: Previous hammer prices for coins of similar condition have varied, but the range seems to be between 40 and 110 euros, with some exceptional cases.

Based on these factors, an estimated maximum purchase price for this coin could be in the range of 100 to 120 euros. This is based on the auction history and the current condition of the coin. However, since the starting price is 30 euros, there may be opportunities to acquire it at a lower price if competition in the auction is not high.