To estimate a maximum purchase price for the coin in question, we can analyze the provided data:

1. Current starting price: 60 euros.
2. Average starting price in previous auctions: 87.63 euros.
3. Average hammer price in previous auctions: 123.2 euros.
4. Hammer price history: Hammer prices have varied, with a maximum of 170 euros in previous auctions.

Since there is no information about the condition of the coin, it is difficult to make an accurate estimate. However, we can consider the highest hammer prices and the average hammer price to establish a range.

- Maximum previous hammer price: 170 euros.
- Average hammer price: 123.2 euros.

Considering that the starting price is 60 euros and that the average hammer price is significantly higher, we could estimate a maximum purchase price that is within a reasonable range above the starting price, but does not reach the historical maximum.

A reasonable estimate could be between the average hammer price and a bit more, considering that the coin may not be in the best condition. Therefore, an estimated maximum purchase price could be:

Estimated maximum purchase price: 130 euros.

This price reflects a balance between the average hammer price and the potential of the coin in the market, taking into account the lack of information about its condition.