Not long ago I paid $400 for a Zenith from that exact era in far better condition. It was higher jewel count, higher finish movement in a gold filled case, I would say worth quite a bit more. The watch you're looking at, unless its solid gold, wouldn't be worth more then $300 in Canada. So maybe 200 Euro.
Having said that, stuff like that does sell for more in Europe than over here. I was in Italy last year and watches I paid a few hundred for in Canada were often as much as twice as much when I saw them over there.
So, 300 - 400 Euro? For 500 I would expect a lot better.
Sorry I don't have a photo of my Zenith..... it went in a trade for a nice Omega.