A smidgen more info... since I see an additional four digit code on yours, I went back and looked. Mine both have a code in the same location.... # 3153 on both springs. Date code?? March 15, 1963?? Am I thinking the wrong format?, or not even a date code?? They were on a '64 car, and sure looked original to me...also, the anti-squeek material between the leaves wasn't plastic or similar, it was like woven white material, like they made the heat shield sleeves with.... no doubt riddled with asbestos?? (looks like yours have it too).
HTH, Lefty71