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

1. Condition: The coin has a condition of 70 (MS-), which is an average condition. This suggests that its value could be in the mid-range of previous auction prices for coins with the same condition.

2. Previous auction prices:
- In previous auctions, the hammer prices for coins with a condition of 70 have varied. For example:
- 2019-10-17: €320
- 2018-12-11: €75
- 2019-07-04: €80
- 2021-06-03: €65
- The highest hammer price was €320, but this may be an exceptional case. Most hammer prices for coins with a condition of 70 seem to be in a lower range, around €75 to €130.

3. Average hammer price: The average hammer price for this coin is €130.73, which can also serve as a reference.

4. Starting price: The current starting price is €30, indicating that there is considerable room for the hammer price to be higher.

5. Estimation: Given that the condition is 70 and considering the previous auction prices, an estimated maximum purchase price could be in a range between €130 and €200, taking into account that the average hammer price is €130.73 and that there is potential for the price to rise in the auction.

Therefore, a reasonable estimated maximum purchase price for this coin could be €150. This allows for a margin of safety and aligns with previous hammer prices.