To estimate a maximum purchase price for the coin that will be auctioned, we will consider several factors, including the starting price, the average hammer price from previous auctions, and the price trends in past auctions.

1. Starting Price: 70 euros.
2. Average Hammer Price: 98.9 euros.
3. Price History:
- It has been auctioned 1295 times, of which 998 have been sales.
- The average starting price in previous auctions is 100.52 euros.
- The average hammer price in previous auctions is 98.9 euros.

4. Condition: There is no information on the condition of this coin, which may affect its value. However, the average hammer price suggests that, in general, coins of this reference tend to sell above the starting price.

5. Price Trends: Observing the hammer prices from previous auctions, it can be noted that there is a trend for coins of this reference to sell above their starting price, especially in acceptable condition.

Given that the average hammer price is 98.9 euros and the starting price is 70 euros, an estimated maximum purchase price could be slightly higher than the average hammer price, considering that interest in the coin may increase during the auction.

Estimated Maximum Purchase Price: 120 euros.

This price reflects a margin for competition in the auction and the possibility that other bidders may be interested in the coin.