Can someone help me?

I have an IWC WWW cal. 83. The mainspring just broke and I need to replace it. I see on some web sites (not all of them) which sell mainsprings that the part for the cal. 83 also works for the cal. 89, and vice-versa.

Is that true? I know what specifications the cal. 83 mainspring are: 1.40 X .12 X 340 X 10,5, but not sure if these are the same for the cal. 89.

Does anyone have an answer as obviously I wouldn't want to put the wrong type of spring in my cal. 83.

Many thanks in advance.

Just a wild guess here as to how to get an answer. Check the IWC parts catalog from 1952 to see if the mainspring for both movements has the same parts number. I've posted the catalog at www.iwcforum.com/Catalogs/1952Fournitures/start.html

According to Dr Ramfft
Cal 89
Cal 89 mainspring is 1.45 x 0.12mm

And for Cal 83 is 1.35 x 0.12mm
Cal 83