As he stated " all functions working fine" and "clean movement" then the watch clearly isn't as described and you have proof from your own watchmaker (in writing preferably).
You are therefore entitled to be compensated a reasonable amount in order to put you in the position you expected to be in. You can claim a partial refund through eBay in the dispute resolution centre. It's in the sellers interest to negotiate an amicable amount as eBay are almost certain to find in your favour.