# Identifying Miyota Auto Movement



## aesmith (Aug 7, 2009)

Hi,

My "new second-hand" automatic has a Miyota movement, partially visible through the glass back. It's marked Miyota, 21 jewels, "Unadjusted" but with no reference number. The watch has full length second hand and date but not day. I can't actually tell if its hand winding, because the watch started running as soon as I handled it.

I think it beats 4 times per second, certainly under a lens the second hand looks like it moves four steps to a second.

Any ideas what movement this would be?

Thanks, Tony S


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## DaveS (Dec 7, 2009)

aesmith said:


> Hi,
> 
> My "new second-hand" automatic has a Miyota movement, partially visible through the glass back. It's marked Miyota, 21 jewels, "Unadjusted" but with no reference number. The watch has full length second hand and date but not day. I can't actually tell if its hand winding, because the watch started running as soon as I handled it.
> 
> ...


Miyota 8215? 21600 bph = 6 bps. Non-hacking, hand winding.

Cheers

Dave S


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## aesmith (Aug 7, 2009)

Thanks. I certainly looks like the picture I've found of the Miyota 8215. I'm really pretty convinced its four beats per second, from watching the second hand movement. I suppose it could be 8, and I'm only seeing every other one, but I really can't see 6 (or 3) steps. Were there any Miyotas with 14400 beats?

Regarding hand-winding, there's no ratchet sound when I turn the crown backwards and it doesn't feel like its winding when I turn it forwards. There's a faint squeeky noise which I guess could be it turning through a seal (its not a screw-down crown). I guess I should let it run down, and see it if really does wind up.


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## aesmith (Aug 7, 2009)

I should add, its a small watch only 32mm across the case (exc crown) so maybe a small movement?


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## jezz59 (Nov 1, 2009)

Hi

Ive done a bit of home work for you, and to satisfy my own curiosity,I own a watch with this miyota mov`t, date only, its a thunderbirds aviation watch (purchased from RLT) in the watches instruction manual the mov`t is described as a CM (Citizen Miyota) 8215, its an 8215 no doubt about it. No info is given about its beat rate BUT, quote " Your watch will start through a Light counter/clockwise winding of the crown(max 5 repetitions!) and now as you wear your watch it will automatically self wind. (note manual overwinding can cause peremenant damage)" end quote. On a final note, it definately manual winds, evidently a feature intended to start it off initially, Ive manually wind mine up several times, and more than five turns with no problems.Hope this helps.


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## aesmith (Aug 7, 2009)

Thanks Jezz. What does the beat on your watch look or sound like? As I say, mine definitely looks as if it moves four steps per second when I watch the second hand with a lens. I guess possibly that could be every other beat, although it doesn't look like it. I really struggle to see how it could be 3 or 6 steps per second like the Miyota 8215, but I can't see any physical differences between my movement and the pictures. It just doesn't make sense.


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## jezz59 (Nov 1, 2009)

aesmith said:


> Thanks Jezz. What does the beat on your watch look or sound like? As I say, mine definitely looks as if it moves four steps per second when I watch the second hand with a lens. I guess possibly that could be every other beat, although it doesn't look like it. I really struggle to see how it could be 3 or 6 steps per second like the Miyota 8215, but I can't see any physical differences between my movement and the pictures. It just doesn't make sense.


Hi, Just been trying to count the beats, its on my wrist today! to be honest i simply cant tell! but have been googling, theres actually shedloads of info about the miyota family of automatic mov`ts. Theres no doubt in my mind that its a 8215 and wikipedia states its beat rate is 21,600 @ six beats/second, other sites describe an indirect second drive which may cause and eratic looking movement of the second hand,(which incidently mine does, never really noticed before!) this does not affect accuracy, also a 45 hour (phenomenal!) standby time is described. So the next step if your really concerened is to see what if any other miyota mov`ts have the single date only and make comparisons, im 99.9% certain its an 8215, these movements have been around donkeys years and theres loads of info.

all the best Jezz


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## aesmith (Aug 7, 2009)

Cheers, I don't doubt that the 8215 is 21,600bph, there's plenty of documentation to confirm including reference manuals on Citizen's web site. My watch has the indirect second hand symptom as described, and as looking through the display back I can't see any physical difference between mine and the photos of 8215s.

Its just this beat thing puzzling me, watching the second hand through a lens I can count the steps one-two-three-four and it stays in phase with the seconds marks all the way round. What I'm wondering is if its actually 28,800bph and I'm seeing every other beat. Some of the smaller Miyotas are 28,800. I was even looking on Youtube but all the videos showing movements in motion are overlaid with pop music so you can't hear the beat.


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