albertofenini,
I want to say that there is a tool for extracting the plastic 'logo" inner faceplate that you are talking about, but I don't know for sure. If you pull the plastic plate, you are liable to break it.
The best advice to remove it may come from "Seiko Kid", as he knows a ton about the materials that make up the Seiko watch cases.
When I do a restore on a Seiko 0532A caliber, I just tape the inside of the case up, that way I do not get any 'cerium oxide" or metal pieces lodged in the nooks and crannies of the bezel between the logo and the case.
Anyway, since the watch case is "gold Plated" you will extremely limited as to what you can use to polish the case as Seiko's gold plating is complete crap! I would try a product that will buff the gold surface like a product we have here in the US called Semi-Chrome, you could also try cape Cod cloths which are designed to buff to a shine on gold plated metal. You could also use automobile "scratch remover" such as Blue Magic
Metal polish cream followed by Nu Finish Scratch Doctor. The practice of buffing gold plated metal to a shine is taking away some of the gold plated surface little by little, and it might just rub completely off in some areas, so be careful. I will caution you NOT to use sand paper or anything abrasive to remove deep scratches are you will be sorry in a hurry. The Seiko gold plating on these watch cases from the 1970's is pretty thin.
Anyway, I hope this helps.
- Patrick