To estimate a maximum purchase price for the coin in question, we can consider several factors based on the provided data:

1. Current starting price: 45 euros.
2. Coin condition: 70 (MBC-), indicating an acceptable but not excellent condition.
3. Auction history: The coin has been auctioned 2 times in the past and sold on both occasions. This is a good indicator of demand.
4. Average starting and hammer price: The average starting price is 110.5 euros and the average hammer price is 139.5 euros. This suggests that, in general, coins of this reference tend to sell for significantly higher prices than the current starting price.
5. Previous hammer price: In the 2015 auction, the coin sold for 220 euros with a condition of 90, which is notably higher than the current condition.

Given that the current condition of the coin is lower than that of the previous auction, it is reasonable to adjust the estimated price downward. However, the fact that it has sold in the past and that the average hammer price is considerably higher than the current starting price suggests there is potential for a higher hammer price.

Taking all these factors into account, an estimated maximum purchase price could be in the range of 80 to 100 euros. This reflects a balance between the current condition and the price history, as well as the demand observed in previous auctions.