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

1. Condition: The coin has a condition of 70 (MBC-), which indicates that it is in relatively good shape, but not of the highest quality. This may influence its value.

2. Previous auction prices:
- In 2014, the coin was offered with a starting price of 1200 euros, but no final price was recorded, suggesting that it did not sell.
- In 2016, the starting price was 160 euros, with an estimated price of 200 euros and a final price of 450 euros. This indicates that, despite a lower starting price, the coin sold for a considerably higher price.

3. Average starting and final prices: The average starting price is 475 euros and the average final price is 450 euros. This suggests that, in general, coins of this reference tend to reach final prices close to these values.

4. Current auction situation: The coin has a starting price of 65 euros, which is significantly lower than previous starting prices. This could attract more bidders and potentially increase the final price.

Taking all these factors into account, an estimated maximum purchase price could be in the range of 400 to 600 euros, considering that the condition is good and there is a history of final prices suggesting that the coin may reach a higher value in the current auction.

Therefore, a reasonable maximum purchase price could be approximately 500 euros.