Genuine matrix blocks are hard to find unless you can scavenge them from an old equipment closet in an office building. They take up a lot of space, so at AT&T we used to make our own, to save space on our backboards. Our home-made model fit right in with the rest of the 66-type blocks, and were easier to label and to maintain.
A diode matrix block can be made very simply and neatly from a 66B-25 or -50 block. Release the tabs on the back, and slide the back of the block off, and dump out and discard all the metal pins. Then take a 66M-50 and do the same, but carefully collect the pins from the M block.
Then put the two-position pins from the M block back into the B block, so that there is a space down the middle with no pins (what would be rows "C" and "D".) Take a bunch of diodes and terminate them in the empty space, one lead on row "B" and one lead on Row "E". The pins at row "F" can be looped...as many as needed...and sent to a station's CMB lead. The pins on row "A" come from the line card CMB leads. Don't forget to face all the diodes the same direction, (cathodes facing to the right) and to wire the ringers for "no capacitor".
The wiring convention we used for those 12,000 sets in one hospital was a single green lead from the 400D card to the matrix, and a single red lead from the matrix to the set's Slate/Yellow lead. The ground return (set's Yellow/Slate) was a single black wire to a 66 block that was nothing but ground.
