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

1. Current starting price: 40 euros.
2. Coin condition: 70 (MBC-), which is a fairly good condition, although not the best.
3. Historical data:
- In the past, this coin has been auctioned 3 times, of which it has sold 2 times and not sold 1 time.
- The average starting price in previous auctions is 134.42 euros.
- The average hammer price in previous auctions is 448.83 euros.
- In the auctions of 2012 and 2013, the coin sold for 448.83 euros with a condition of 90.

Given that the current condition is 70, which is lower than the condition of 90 from previous auctions, it is reasonable to expect that the hammer price will not reach the higher levels observed in the past. However, the current starting price is significantly lower than the average starting price and the average hammer price from previous auctions.

Taking all these factors into account, an estimated maximum purchase price could be in a range between the average hammer price and the current starting price, adjusted for condition.

We could estimate a maximum purchase price around 200-250 euros, considering that the condition is lower than that of previous auctions, but still, it is a coin that has shown good interest in the market.