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

1. Starting price: 90 euros.
2. Average hammer price in the past: 160 euros.
3. Condition of the coin: 75 (MBC), which is quite a good condition.
4. Auction history: The coin has been auctioned once before and sold for 160 euros.

Given that the average hammer price in the past was 160 euros and considering that the condition is the same (75), it is reasonable to assume that the hammer price could be in a similar range.

Additionally, since there is an auction scheduled in the coming days and the coin has a history of successful sales, this could increase interest and competition among bidders.

Taking all these factors into account, an estimated maximum purchase price could be around 160-180 euros, as this reflects the previous hammer price and allows for a small margin for competition in the auction.

Therefore, an estimated maximum purchase price would be 180 euros.