thanks group, the speedometer makes sense. Now I have to figure out how to get it out of there. I made a wood dash for my early mini and the gauge was in the dash as it was installed. So I have to pull the dash.

I will take the unit apart and see what is stuck inside. This is a replacement NEW unit with 4500 miles on it.

Jerry

As Dan said... the problem is internal to the speedometer.  If you are not intimidated you can disassemble, clean, and re-assemble this yourself.  If you are more comfortable sending it off for repairs there are several shops that handle Smiths gauges.

The list below is what I always post if someone want to try DIY repairs:
    Download, print out, and read the 27 page PDF by Anthony Rhodes.  It explains how the speedo         works and what you will find inside.
    Work on a clean white sheet in a well lit area. 
    Draw sketches and take pictures as you take things apart so you will know how/where they go
        back together.
    Work slowly.  

Ignore the drivel.
A broken gear at the transmission end would result in a reading of 0 mph.
A disconnected cable (either end) would produce the same result.
A kinked or sticky cable would produce a rapidly fluctuating reading with your true speed somewhere in the middle of the indicated range.
The cable is not directly connected to the needle of the speedometer, but uses a magnetic field to move it. The spinning cable spins a magnet whose magnetic field tries to spin an armature attached to the needle. (They don't physically touch.) The needle has a watch spring to return it to zero. The faster the cable turns, the more magnetic force is exerted against the resistance of the spring, so the needle is actually indicating that force. For a given car speed, we read a scale that happens to be marked in mph or kph.
The speedometer needle is on a shaft with very fine bearings, so most likely the bearings have worn or got dirty, or the spring has broken.
As you drive, does your odometer continue to count? It is driven by gears turned by the speedometer cable.

Jerry ,
i feel so sorry to hear about your dilema, sometimes there’s a point in our lives that tragedy may happens, and sadly they are beyond our control. Prayer is the answer. Just be thankfull that diring the times that your speedometer was not working ,The police did not stop you for overspeeding.
Very seldom that classic mini reach the speed of 50miles per hour, that’s probably why your speedometer got stuck at that speed, its not used to it. Btw what mini do you have?
Again, i sympathize with you during this difficult times.

What are the betting odds on a stuck speedometer: 1. The cable has a problem 2. the speedometer has a problem 3. The drive gear has a problem.

I am hoping for #1 and I think the odds are slim for #3. Driving back from the gym yesterday and I was doing 50mph standing still. sigh, and everything was working so well.

Jerry