The Two Horse brand patch was implemented in 1886, sixteen years after Levi Strauss and Jacob Davis patented the copper-riveted waist overall.
Do they have a lemon yellow waistband stitch single stitched? From 1937 onwards, the rivets on the back pockets were sewn so that they were only visible from the inside, due to consumer complaints regarding scratching furniture and saddles.
The stock 501, on the other hand, is geared at a budget consumer who still needs a good-fitting, durable pant.