Thank you Gentleman.  So, BW and HS on some vintage and I gather all antique time pieces, were to be (in pair ) vibrated to the design beat . Two BW on same assembly line were dynamically different even though they weighted and looked the same. If a HS for a rare collectible pieces is needed, I think one can be extracted from other( not so collectibles) members of the family and true would then need to be vibrated with the BW anew. I have been finding hairsprings in the family, th