Twins came out in the 70's and were a precursor to the multimode blade carts. Think of two thinner Schick injector s stacked closely on top of one another. They are liked by some, my heavier beard clogs them up. I think they are still made in Japan and command a premium for a also shave. You can find them floating in the Bay NOS as well
It's like two blades glued together. I don't know that's how it's made but that's what it's like. Thick! Great blades but they only fit later Schick injectors. I've forgotten precisely which razors. Not the G or anything earlier. They fit the L and everything after than for sure. I use 'em in the L and in the M and in the O.
The regular yellow Schick injector blades (not the TWIN) are quite good according to me. Great in the E-2!
TWIN blades are hard to find and expensive but boy do they last and last and last. Incredibly long lasting blades. You almost only need one.