Need white thread 1960’s

[Laneylaney]

I started a bedspread after married 1961. Didn’t finish “Rose Bower Beadspread” now want finish. Can’t find correct white thread. Clark’s O.N.T. Mercerized thread, white. 
Help Elaine

[Granny Square]

Hi, welcome to the 'ville.  I think you probably already know this, but you are not going to find that very same brand.  Even if you did, it likely would not be the same dye lot --I mostly work in doily thread nowadays, and have had dye lot problems happen even with the same brand running out mid-doily, but recently had a happy unexpected 'run-out' of a ball and happened to have a different brand on hand that matched pretty well, so you might get lucky.  

Probably the closest you are going to find is Aunt Lydia's, which is the surviving Coats and Clark mercerized thread brand.  I'm assuming your project is size 10 thread, which is probably typical for a bedspread?  Their thread comes in smaller balls (without looking it up, I think they're 400 yards) and huge  balls which are about 3x that.  If you are in the US, Michaels and Walmart carry it, plus you can buy it at yarnspirations.com (which is a site that represents a company that owns most of the US yarn brands now).