Hallo Bo.
You saund as if you believe the Seeley frame is build with/from  parts of the original Honda frame!?
Can't you be told the frame number of the Seeley frame used?
I'm kind of interested as my Sand Cast too was transferred into a Seeley frame in '78.
It is indeed difficult to understand the wording for a photo in here when no knowledge of used words!

4pots 1969.
Had this friend of yours had sticking throttle slides?
In my day I was the only one in town on a CB750.
So never really had anyone to talk "daily" problems with.
Think I have a post card dated Oct '69 from Honda.
They had forwarded my problem to the distributor of my area!
Not a word about what it was.
Come to think about it now some explaining of holes in centre of clutch hub to ease plate separate!
Neither do I remember having been called to dealer for some help.
But of cause I had been to dealer asking for help before writing to Japan.
Just felt they had no detailed knowledge of this new bike on the market.
More or less similar to my present day ride: a Fireblade.
Now 170K km had gear change problems from day one, now more than 20 years ago.
Dealer just told me to learn to change gear properly when on a Honda!
And I had at the time done maybe half a million km!
Though mostly on a flat twin BMW.
Sandcast got a Seeley frame after '78. That made it a delight to ride.
With 4 into one exhaust. Pipes don't touch so easily.
Engine of the Blade runs silky smooth as ever.
But it jumps out of fourth gear! Not on the overrun though.
After 10 years I wrote to Japan asking them to tell dealer what to do.
Was duely answeed: go to the Honda of your area, Where of cause I had already been.
Then a friend advised me on to Fireblade.org.
A handful of owners had similar problem!
And solutions which I was not quite sure of interpreting correct.
Went to the dealer with this knowledge.
He just asked me to leave his place and ask those people for help!
Erling.

Might well have some opinion.
For my part I mostly learn about a motorcycle I've had for 47 years, in 3 week time!
And not really know inside out of!
In other words, don't think I can ad to the knowledge in this  forum.
Erling.

On my tank these numbers say: 4 6 2!
What to make out of that?
Oil tank say 5 2 7.
Erling.

James May says his exhaust bafflers are removable!
Erling.

The set with the longer cables have them opposite to one another.
Which to me at least looks as original!
Erling.

+1
Erling.

Hallo Bo.
I'm situated 50 km south of Helsingborg/Elsinore on the opposite Danish shore.
København to be exact.
Rumours will have it owner of the first CB 750 of Norway carries the same name!
Sorry I did not point out my nationality in my "45 year story".
Erling.