If it's the one I'm thinking of it's like this one on Ebay.

http://www.ebay.com/itm/Cessna-ARC-R-402A-Marker-Beacon-Receiver-GC-/231013599334

It mounts remotely and the lights can be mounted anywhere, but Cessna mounted them in an existing bracket behind the plastic fascia in the eyebrow of later 150's (left side of the rear view mirror). Engraved fascias are available. Along with installing the com switches in the right side fascia, the need for a separate com panel/marker beacon receiver is eliminated, freeing space in the radio stack. I did this on Russ Anderson's Aerobat years ago, so we could mount a second MX-300.

[Linked Image]

http://g-awaw.org/