1940's Carhartt Lace Back Salt & Pepper Chambray Pants

If you didn't already know, these fantastic work pants sold on eBay for a whopping $1,550. I've seen them in denim before, but not in chambray (apparently there was another pair listed earlier in the year I missed). Wish I had a few of these to sell...and one to wear! Oddly, the seller said that Carhartt could not find these in their catalog archives and thinks they could be a salesman's sample? I think the simple fact that other pairs were floating around on eBay would probably negate this theory. They probably just went out with a really low production run OR just never made in a catalog (perhaps Carhartt's archive is also not that complete either).