The best way to deal with a tight case back is to glue a nut on it. When it dries I use a spanner to open it. After I dissolve the glue in methylated spirit.

Movement looks to be in excellent condition.

No doubt the watch needs a service.

The Patent Pending case back dates this watch between 1958 and May 1960.

The dial and hands are in very good condition!

Hands and dial removed and you can see the setting/winding mecanism

Movement coming apart.

Here you can see the gear train layout.

Old mainspring.

All the parts cleaned and ready to be put back together.

I see that the balance moves freely after fitting the shock jewels.

Here you can see the great train before fitting the train bridge and barrel bridge.

I fit the winding/setting mechanism, Certina has a great movement finish.

Almost back together.

The balance is back in palace and the movement is ticking like it should.

Watch performs very well.

Movement back in the case looking great! The movement case ring is cushioned against the case using a thick rubber ring.

Great looking classic!

I would wear this any day!