my newest is actually my oldest, well as in that I bought it new when I got out of high school in 1978, and there is not much stock about it now.
1978 Huffy Good Vibrations (could be the only one of it's kind rolling on Lobdell hoops and New Departure hubs.
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it looked like this when I got it 41 years ago.
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Now the Huffy isn't really a collectible bicycle, it just has a permanent spot because I still have it, and it has been stole twice, only to come back home both times.
The newest collectible would be my 1963 Otasco Flying O Lancer.
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then my actual oldest in age is either my 1929 Westfield GJ-1 Roadster or my 1920's Pierce BR Amateur Sprint Racer, as it is really hard to nail down a date the Pierce's, it is what it is.
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All of my bikes are ridden regularly.