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Need Dimensions for Patek 10-200 Mainspring

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Hi folks, I’m just wondering anyone has this info handy. It looks like 1.20x0.11x10”…’ish. I am basing that on the barrel dimensions.

I realize I can buy one but wanted to get the dimensions so I can see if I might have one that will work. It’s a standard mainspring, nothing special…Thank you, in advance.

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I’m not shocked that nobody has been able to help me with this question. The Patek mainsprings are not in any Bestfit (or the like) catalog that I have ever seen. 
The mainspring (even generic) is quite expensive to purchase, which isn’t surprising, either.

The barrel ID is 8.7mm and the arbor is about 2.8mm. I’ll have to guess a little on the strength and length balance but I’m sure I can find something close. Based on the dimensions I provided, can someone tell me what size ms they would put in it? My new estimation is 1.20x0.10x11.5”

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 what happened to the old spring?

according to the website below no parts are available but they do give a mainspring listing not sizes unfortunately. Then taking that number to the home page looks like it's available cheaper than eBay.



3 hours ago, Woolshire said:

The Patek mainsprings are not in any Bestfit

because I was curious about the number I found up above I looked at bestfit online. Here's what I found out that looks like it's the right number unfortunately because it's an original spring we don't get any dimensions.



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this is what happens if you don't fully do all of your research. I found the safe answer I found your exact caliber we got a mainspring number we got a price at a decent price for the original spring verified that the spring number at least on bestfit agrees with what we have so it was safe

yes I did look in the GR catalog I had seen that 200 watch has a spring similar to what you perceive it should be. But to be honest I never looked at the 200 watch to see what its mainspring was.

then the other amusement I went back to the bestfit online because if the 200 have the same spring I were to see that when I snipped out the image up above. Turns out they don't even show a 200 listing at all.


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Not sure what the comment on not doing my research is about but I likely will order the mainspring from Borel that you found and thank you, again, for that.

I have 100+ BestFit mainsprings that I would like to look through to see if I might already have the correct ms…that’s why I’m still digging.

Earlier, John asked what happened to the old ms. Well, I wish I knew. I lost it! I took this watch apart for servicing a couple months ago and it had a steel ms, so it was getting replaced. Then I found a future potential issue with the set lever (nib was slightly worn/short). My goldsmith friend was able to laser weld a tiny bit of steel on. I’m now putting it together and can’t find the ms…but the set lever works great!

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