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 70 (VF-), indicating that it is in acceptable condition, but not among the best qualities. This may influence the price, as coins in better condition tend to reach higher prices.

2. Auction History:
- The coin has been auctioned 16 times, of which it has sold 15 times. This indicates good demand.
- The average hammer price is 36 euros, providing a solid reference for the coin's value.
- Looking at previous hammer prices, it can be noted that in auctions with similar conditions (70 and 75), the hammer prices have varied but have reached up to 55 euros in some cases.

3. Starting Price and Average Starting Price:
- The starting price is 20 euros, and the average starting price is 25.44 euros. This suggests that the starting price is reasonable and could attract bidders.

4. Recent Trends: In the most recent auctions, hammer prices have been in the range of 30 to 45 euros for similar conditions.

Based on these factors, an estimated maximum purchase price could be in the range of 40 to 55 euros, considering that the coin has good demand and its condition is acceptable. However, since the average hammer price is 36 euros, a more conservative maximum purchase price could be around 45 euros.

Therefore, a reasonable estimated maximum purchase price would be 45 euros.