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

1. Starting price: 750 euros.
2. Current condition: 95 (EBC+), which is a high condition.
3. Auction history:
- In October 2021, a coin with a condition of 90 sold for 900 euros.
- In December 2021, a coin with a condition of 95 sold for 1200 euros.

Given that the condition of the coin to be auctioned is 95, and considering that in the past it has sold for a hammer price of 1200 euros in a similar condition, we can infer that the hammer price could be in a similar range or even higher, depending on the demand in the current auction.

The average hammer price in the past for coins of similar condition is 1050 euros, which also supports the idea that the hammer price could be in that range.

Maximum purchase price estimation:
- Taking into account the highest previous hammer price (1200 euros) and the average hammer price (1050 euros), a reasonable maximum purchase price could be in the range of 1100 to 1200 euros, considering the high condition and the potential interest from collectors.

Therefore, an estimated maximum purchase price could be 1200 euros.