I knew I had an SSI chip here somewhere: SSI 201, the DTMF decoder I liberated from my Apple-Cat II modem when I sold it (30 years ago!) http://www.downloads.reactivemicro....AppleCat_II_Modem/Pics/AppleCat%20II.jpg

I opened the lid and took some pics: http://www.seanriddle.com/ssi_201_metal.jpg

It has the same layer ID text, as well as the "square, square, square, square, octagon" test pads that the Battleship and Simon chips have.