This looks to be a vendor-programmable remote.

It comes with 4 AAA batteries installed. Under the battery cover is a hole for an 18 pin chip, "Microchip" brand - I mistook it for the Motorola M at first. The chip's socket is on the back of a board with a capacitor, a resistor and the battery connections. I'm guessing they flash this chip for whatever logic is needed to output the right IR signals for a given remote. Two IR LEDs on the front of the remote.

The top button area has common/universal things: Power, input, sleep, channel +/-, disp, volume +/-, mute, menu, recall and a number pad. Also a little red LED that lights up when you press a programmed button.

The bottom section has a translucent sliding cover (labeled "REDI REMOTE") covering a 5x7 field of tiny buttons. Features specific to the old remote are placed in this field at the same places as on the old remote. This leaves 15 unused/unlabeled buttons in my case. A printed label for the button functions covers the field with a plastic overlay. I need to be careful not to crunch it (again) in the sliding cover.

Now I don't have to get off the couch to adjust the volume when it shifts from song to song on old mix tapes. Although flipping the cassette over is still a manual operation ;).