Service Eterna calibre: 820H

Eterna calibre 820HBefore Eterna became famous for their Eterna Matic movements they had a very nice bumper movement. This is my first bumper automatic and I’m exited to see how it works.IMG_2724Movement is in excellent condition for a watch this age.IMG_2947No doubt that a service is needed.IMG_2948I start by removing the automatic bridge so that I can remove the pivoting weight.IMG_2949Here you can see the springs that absorb the shock of the pivoting weight.IMG_2950Here you can see the ratchet lever (gold part))  that transferee the power from the pivoting weight to the ratchet wheel.IMG_2951The underside of the ratchet lever.IMG_2954The movement ready to be taken out of its case. Note the early shock protection that Eterna used.IMG_2955The movement out of the case and I remove the cock that holds the sweep second arbor in place.IMG_2956The dial side of the base plate you can see the setting mechanism and the other shock protection device.IMG_2957The varnish has faded and tuned yellow brown. The original luminous compound is still on the dial and great care must be taken when cleaning.IMG_2958I take a risk and give the dial a mild clean and varnish for protection.IMG_2960And the risk pays of!IMG_2962I remove the balance and with these old shock devices I need to remove the complete balance to be able to oil when assembling the watch.IMG_2970Old mainspring.IMG_2965Here you can see the gear train.IMG_2980Here are all the parts after having been cleaned.IMG_2981Upper and lower shock device.IMG_2993Testing that the balance moves freely.IMG_3278I have souced a NOS mainspring that I useIMG_2966Movement coming back together nicelyIMG_3013Base movement almost back togetherIMG_3031Dial side of the movement before putting the dial onIMG_2972After a closer inspection I see that one of the hands has gotten new luminous compound at one point.IMG_3021As the lettering on the dial has aged patina I decided to experiment with tea to get a darker colour on the luminous compound. I start of by mixing the luminous compound in tea.IMG_3019It is important to wait until the compound is completely dry before mixing it with binder.IMG_3022The compound applied to the hands.IMG_3032Dial and hands back on the movement and I feel I hit the colour pretty well. Note I love that Eterna has a red marker on the second hand. Feels a little sportyIMG_3035Movement back in the case.IMG_3018Performance is goodIMG_3037I think this watch looks very good.IMG_3039If anyone is wondering the compound still lights up after the tea treatment.Eterna calibre 820HThe 34mm case makes this 40’s classic very nice to wear;)

13 thoughts on “Service Eterna calibre: 820H

  1. Sorry for taking up this old post. I recently acquired a watch with a closely related movement myself and have now got a question about the shock devices. Your post shows that it is possible to remove those for cleaning. Now I wonder why it was necessary to remove the balance spring from the cock for oiling. Can you help me?
    Thank you and kind regards

  2. Hi, Lovely job.

    I have one of these but the movement is loose in the case. I think this is because the piece of metal that is screwed to the back of the movement (and which presumably pushes against the watch back) is missing.

    Do you what this part is called?

    Kind Regards,


  3. What did you use to re-varnish? I once tried nitrocellulose (Zaponlack” in German) which dissolved all the printing. Another near-death in amateur hands.

  4. Great job on the movement and an excellent restoration of the hands and dial. It has an interesting anti-shock system with the jewel and its carrier sliding in a slot whenever there is a jolt. I’ve never seen that type before. Thanks for posting.

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