Good questions John. Buying the right thread to restitch a helmet in general is a large problem when you get into this. I am a dufus regarding trying to understand the information found on the labels of spools of vintage thread. First, it must be 100% cotton, no man made additions. This forces you into the world of vintage thread especially for the OR’s helmets which have a thicker gauge of visor thread . Any modern thread of appropriate thickness is going to have nylon in it, so forget it. EBay is a good source for vintage thread. The thread for officer visors is naturally finer to match the stitching. I will post some pictures of my spool labels. The thread used to stitch in an OR’s liner would be the same as used on the visors. The officer sweat band is tack stitched using a thick white saddle type thread. The officer silk is stitched with a fine 100% cotton thread coloured to match the original as best you can. All thread must be coated in beeswax as you stitch! Any stitching in leather has to be waxed. When looking for “natural” thread, one would also think of 100% linen. This type of linen thread is still used in vintage/antique book binding and can be tracked down on the net. I have not had much luck with linen, even though I always thought of it as very tough. In my experience using it to stitch visors, it frays and breaks......very frustrating! So not for me. Again, I will post photos of those spool labels . I am sure that our European stitchers will provide more information.
So the pictures of my vintage thread spools.....wow we are really getting down to the fine points here!
Left spool, for officer visors, fine thread, on the right the heavier thread for OR's visors.
The back sides...the Dorcas is a 12 cord thread.
Two other spools of vintage cotton thread. The thicker vintage threads are the hardest to find as the ladies of the past would have naturally bought finer threads for their clothing repairs. Coats is a famous Brit Company still in production today. The numbers 40 and 10 would suggest that the lower the number, the thicker the thread.