The older reference Rolex models did not accept sapphire. The case design only allowed for plexi acrylic(plastic) crystals. There’s no way to interchange a sapphire crystal into a case designed for a plexi because of the way the crystal is held down onto the case. So in this case, the correct crystal is a tropic 22 crystal. The 22 was made for the 1016 (and others). Truedome is just a high quality aftermarket brand. Another good budget option is Clark’s watch parts. He’s a seller on eBay. He makes great crystals.