To estimate a maximum purchase price for the coin that will be auctioned, we can consider several factors based on the provided data:

1. Starting price: 120 euros.
2. Auction history: The coin has been auctioned 119 times, of which it has sold 99 times. This indicates a good sales rate.
3. Average hammer price: 47.27 euros, which is significantly lower than the current starting price.
4. Previous prices: The starting and hammer prices of previous auctions varied considerably. For example, in recent auctions, hammer prices have reached up to 140 euros, but there are also many cases where the hammer price was much lower.

Since there is no information about the condition of the current coin, it is difficult to make a direct comparison with previous auctions. However, we can observe that in past auctions, hammer prices have fluctuated quite a bit, and the current starting price is relatively high compared to the average hammer price.

### Estimation of the maximum purchase price:
- Considering the starting price: 120 euros.
- Taking into account the average hammer price: 47.27 euros.
- Observing the highest hammer prices in the past: up to 140 euros.

Given that the starting price is 120 euros and considering that the highest hammer price has been 140 euros, a reasonable maximum purchase price could be in the range of 100 to 120 euros, depending on demand and collector interest.

### Estimated maximum purchase price:
100 - 120 euros.

This range allows for competitiveness in the auction without exceeding the starting price, considering that interest may vary.