To estimate a maximum purchase price for the coin in question, we can analyze the provided data, especially the previous auction prices and the context of the current auction.

1. Current starting price: 250 euros.
2. Average hammer price in the past: 269.58 euros.
3. Previous hammer prices: The highest hammer prices in recent auctions have been 380 euros (on several occasions) and 360 euros.
4. Condition: There is no information about the current condition of the coin, but in the past, many coins of the same reference have had a condition of 95, suggesting they could be in good condition.

Given that the average hammer price is 269.58 euros and considering that in previous auctions hammer prices have reached up to 380 euros, an estimated maximum purchase price could be positioned in a range between the average hammer price and the highest observed price.

Estimated maximum purchase price:
- A conservative price could be around 300 euros, which is slightly higher than the average hammer price.
- A more optimistic price, considering the highest prices reached in the past, could be up to 380 euros.

Therefore, a reasonable maximum purchase price could be between 300 and 380 euros.