@Miserere,
your 2.8/28 looks very similar to Cosina's making of this lens, aka Revuenon aka whatnot-company. Focusring and aperture ring look the same. Aperture clicks on this one are on the heavy side, right?
One more from the legions of forgotten lenses,
Meyer Görlitz Telemegor 5.5/180 M42-version.
Very handy lens, top daylight walkaround lens. Exotic and not loved, but worth a try. You'll get a soft glow lens with flare (wide open) ,
direct link don't work, gotta klick here, sorry
... and I love flare, so here we go (f/11),
... but some decent IQ also, even wide open (well f/5.5 is 'wide open' :-). BTW I dislike this bokeh, but many people might find it attractive :-)
direct link don't work, gotta klick here, sorry
Make the best of what you've got, it's so much more fun than nitpicking bads and whats and ifs of your gear,
Georg (the other)
PS: Seemingly now it's possible to post Picasa-pics (from search results) into here, great! But: Only full size. Please tell me if this is too big for you screen.
PS edit: Seemingly not always, links inserted