just what i've gathered over the years:
the metal head tube badges were on MC2 era bikes (1994-1996) officially imported to Europe to differentiate them from the grey imports.
the US Kleins did not have any head tube badge or sticker until 1997.
EXCEPT for the early team bikes like the Storm Adroit. those were not meant for the market. as on all team bikes the brand logos and names are all over the place so that everybody can see them easily.
the only other regular exception i am aware of is the 1996 Mantra Pro which had a yellow head tube logo.
i dont know why some got silver and others golden metal badges. i've heard once that the 20th anniversary edition for the Swiss market got silver logos and the one for the German market golden logos (or the other way around). maybe the color of the head tube badge follows such a pattern too, no idea.
the Graffiti Attitude has that metal badge because the owner has put it on.
the Attitude in the first pic seems to be a regular 1996 Attitude which shouldnt have a head tube logo. it looks so different than anything else i have seen so far (from the little that is visible) that it might be something self made.
but there are so many odd-balls out there, one-offs from Klein employees, team bikes etc. that it might be genuine.
or the photo is just unlucky and it is the logo that all Kleins had from 1997 on, like this Adroit or the Mantra Pro already in 1996
in that case i would speculate that it was painted late in 1996 and got the logo like the other bikes, maybe because the painter liked it or a customer had the power to get it on there.
such a logo was on all post-1996 Kleins afaik, like on the black Adroit.
the logo on the red Attitude looks odd color wise but otherwise seems to be the normal logo. but maybe that was the lettering color for that model. i dont know many details of these late Trek Kleins...
there's one other variety on some Trek Kleins which is just a thick sticker like on this one
i have a few of these stickers but don't know the story behind them. somebody once has told me that they were used on repaints but i'm not sure if that's always the case. i know repaints that have painted logos and original paints that have that sticker. maybe just another idea of a designer that did not survive...
i am sure there are more exceptions but that's roughly what i think to know.
carsten