I help need to identify the correct mainspring for an Omega Cal 613 wristwatch

Serial No. 26725253 dating it to 1968.

I have searched the main UK material house but keep coming up with No. 600 spring.

I have no reference details to check if this is correct.

Any advise would be appreciated. Also any idea where to purchase this spring.

Mike

Ofrei would confirm your choice:

http://www.ofrei.com/page_141.html

You could buy it here.

Thanks a lot Dave.
I looked there but didn't spot it.
It seems that the same spring fits quite a few different calibre.
Problem solved.
Thanks again, Mike