To estimate a maximum purchase price for the coin that is going to be auctioned, we can analyze the provided data, including the starting and hammer prices of previous auctions, as well as the condition of the coin.

1. Current starting price: 90 euros.
2. Average starting price in the past: 38.58 euros.
3. Average hammer price in the past: 60.94 euros.
4. Hammer price history: Hammer prices have varied significantly, with a maximum of 140 euros in a previous auction.

### Analysis of previous prices:
- The coin has had a hammer price range from 9 euros to 140 euros, depending on the condition and other factors.
- The condition of the current coin is not specified, making it difficult to determine its exact value. However, in previous auctions, coins in high condition (95-100) have reached higher prices.

### Estimation:
Given that the starting price is 90 euros, which is significantly higher than the average starting and hammer prices in the past, it is reasonable to assume that the hammer price could be in a higher range if the condition is good.

- Estimated maximum price: Based on the highest hammer price of 140 euros and considering that the starting price is 90 euros, a maximum purchase price could be between 100 and 120 euros, depending on demand and condition.

Therefore, an estimated maximum purchase price could be 120 euros.