I've seen so many wrong dates on bikes.  Of course many things can cause this.  Including bikes sitting unsold into the next year.  Bikes being re-registered and the like.

The K1 has 7 variations so its easy to mistake the model.
There were actually 2 CB450K1's or at least variations which could be classed as 2 separate models. The 1969 is quite different in many
respects.  The blue one is as i found it.it was chromed up a bit in the 70s
and has the 1970 front end which of course were compatible with the cb750.

About 6000 early K1's were made with the small triangular sidecover badge which simply had 450 on it in black.  The triangle below it was in red, the badge was a double layer brass and chromed.  What distinguishes the early K1 is this badge and the 2 horizontal pressed lines above and below the badge the full width of the sidecover.  Also the seat is peculiar to this early version, it is quite flat and has course vinyl covering the top pad (to prevent slipping i guess).  The sides are smooth vinyl, and the piping bordering the two vinyls is white.

Transitional models recieved a thicker padding and pleated top cover.  the sidecovers recieved the new version badge with 450 DOHC and a smooth surfaced sidecover.

The american market models had slimline fenders whereas ours and europe got the deep valanced fenders.

In 1971 the CB450 came out with the CB500/4 front end (fork legs,front guard,brakes and front wheel.)

You have to admire Soichiro Honda for his quest to provide the best product for the best possible price, and his ability to be able to stand by his word to provide any part for any Honda he produced.  Things have changed since his death, now youre lucky to get parts 20 years old, its just not good economics from a new sales point of view.