Speedometer evaluation?

What I know....
Speedometer cables can work fine in warm weather and raise hell in the cold.
99% of speedometer pictures show the head on a table and leaning on its input shaft. When they were new this didn't distort the magnetic field, needle wouldn't move at all. Some are so worn that the needle has climbed to 7 mph in the picture. In that case,, If one part isn't already touching the other, its going to soon enough.
The odometer is direct driven. In the basic odometer, the little planetary gears between the digit wheels are brass, but in the added trip clock, they are plastic. The tenths wheel carries all of them and they put it over on the trip clock. Engineering failed right there? No. it was designed to last 10 years or more. The better question is how many times has the trip clock been hand wound back to zero during 50 years.
I don't see the needle lift in your picture. you might check for it. If a new cable doesn't cure it, disengage the odometer and see if the intermittent problem goes away.
I have 2 67 model rally speedometers here just like yours with tenths wheel worn completely out. Both need only that 1 part that I don't have a source for.
I went ahead and bought a good used 68 speedometer without the trip clock. It will go in my 67 with a new cable when needed. Good luck with yours