Nachtmann indicates in their catalogue wether they used lead crystal or non-lead crystal. I have the box of the second picture, the Slice, and it says 'non-lead crystal'. I believe the third one, Bossa Nova, is also without lead. They still are quite heavy and show no press lines.
The first one though probably is lead crystal and has endured some polishing that looks manual. Older Nachtmann pieces probably were made of lead crystal mostly, if they are labeled they often have a 24% lead label as well.
Visible seems are not really current Nachtmann policy, but I don't know wether they went through a more sloppy period. I know Peill & Pultzer, another German quality crystal factory, did. Some of their 80's vases are thin, seemed, and not high quality. I wouldn't have believed them to be Peill if they weren't marked... Probably a result of frantically trying to find a profitable business model when handmade production had become too expensive at that time.
Anyway, maybe we can conclude that Nachtmann is unlikely, it might however still be German given the style of the design (Germany had a lot of smaller glassworks that in the 80s and 90s slowly faded out of existence or were gobbled up by bigger ones). Czech of course is also still a possibility.
Astrid