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

1. Starting Price: The starting price is 120 euros.
2. Auction History: The coin has been auctioned 17 times, of which it has sold 14 times. This indicates good demand.
3. Previous Prices:
- The average hammer price in previous auctions is 124.36 euros.
- The highest hammer prices in previous auctions have been 190 euros (in 2019) and 140 euros (in 2017).
4. Condition: There is no information about the current condition of the coin, which may affect its value. However, in previous auctions, some coins of similar condition have reached hammer prices of up to 190 euros.

Given that the average hammer price is 124.36 euros and considering that there are previous auctions with higher hammer prices, an estimated maximum purchase price could be in a range between the average hammer price and the highest price observed.

Therefore, an estimated maximum purchase price could be approximately 180 euros. This is based on the trend of previous prices and the demand observed in past auctions.